[ALSA] usb-audio: use usb_buffer_alloc/free

[deliverable/linux.git] / sound / usb / usbaudio.c

/*
 *   (Tentative) USB Audio Driver for ALSA
 *
 *   Main and PCM part
 *
 *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
 *
 *   Many codes borrowed from audio.c by
 *          Alan Cox (alan@lxorguk.ukuu.org.uk)
 *          Thomas Sailer (sailer@ife.ee.ethz.ch)
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 *
 *  NOTES:
 *
 *   - async unlink should be used for avoiding the sleep inside lock.
 *     2.4.22 usb-uhci seems buggy for async unlinking and results in
 *     oops.  in such a cse, pass async_unlink=0 option.
 *   - the linked URBs would be preferred but not used so far because of
 *     the instability of unlinking.
 *   - type II is not supported properly.  there is no device which supports
 *     this type *correctly*.  SB extigy looks as if it supports, but it's
 *     indeed an AC3 stream packed in SPDIF frames (i.e. no real AC3 stream).
 */


#include <sound/driver.h>
#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/usb.h>
#include <linux/moduleparam.h>
#include <sound/core.h>
#include <sound/info.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <sound/initval.h>

#include "usbaudio.h"


MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
MODULE_DESCRIPTION("USB Audio");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("{{Generic,USB Audio}}");


static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;      /* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;       /* ID for this card */
static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;      /* Enable this card */
static int vid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 }; /* Vendor ID for this card */
static int pid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 }; /* Product ID for this card */
static int nrpacks = 4;         /* max. number of packets per urb */
static int async_unlink = 1;

module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "Index value for the USB audio adapter.");
module_param_array(id, charp, NULL, 0444);
MODULE_PARM_DESC(id, "ID string for the USB audio adapter.");
module_param_array(enable, bool, NULL, 0444);
MODULE_PARM_DESC(enable, "Enable USB audio adapter.");
module_param_array(vid, int, NULL, 0444);
MODULE_PARM_DESC(vid, "Vendor ID for the USB audio device.");
module_param_array(pid, int, NULL, 0444);
MODULE_PARM_DESC(pid, "Product ID for the USB audio device.");
module_param(nrpacks, int, 0644);
MODULE_PARM_DESC(nrpacks, "Max. number of packets per URB.");
module_param(async_unlink, bool, 0444);
MODULE_PARM_DESC(async_unlink, "Use async unlink mode.");


/*
 * debug the h/w constraints
 */
/* #define HW_CONST_DEBUG */


/*
 *
 */

#define MAX_PACKS       10
#define MAX_PACKS_HS    (MAX_PACKS * 8) /* in high speed mode */
#define MAX_URBS        8
#define SYNC_URBS       4       /* always four urbs for sync */
#define MIN_PACKS_URB   1       /* minimum 1 packet per urb */

typedef struct snd_usb_substream snd_usb_substream_t;
typedef struct snd_usb_stream snd_usb_stream_t;
typedef struct snd_urb_ctx snd_urb_ctx_t;

struct audioformat {
        struct list_head list;
        snd_pcm_format_t format;        /* format type */
        unsigned int channels;          /* # channels */
        unsigned int fmt_type;          /* USB audio format type (1-3) */
        unsigned int frame_size;        /* samples per frame for non-audio */
        int iface;                      /* interface number */
        unsigned char altsetting;       /* corresponding alternate setting */
        unsigned char altset_idx;       /* array index of altenate setting */
        unsigned char attributes;       /* corresponding attributes of cs endpoint */
        unsigned char endpoint;         /* endpoint */
        unsigned char ep_attr;          /* endpoint attributes */
        unsigned int maxpacksize;       /* max. packet size */
        unsigned int rates;             /* rate bitmasks */
        unsigned int rate_min, rate_max;        /* min/max rates */
        unsigned int nr_rates;          /* number of rate table entries */
        unsigned int *rate_table;       /* rate table */
};

struct snd_urb_ctx {
        struct urb *urb;
        unsigned int buffer_size;       /* size of data buffer, if data URB */
        snd_usb_substream_t *subs;
        int index;      /* index for urb array */
        int packets;    /* number of packets per urb */
};

struct snd_urb_ops {
        int (*prepare)(snd_usb_substream_t *subs, snd_pcm_runtime_t *runtime, struct urb *u);
        int (*retire)(snd_usb_substream_t *subs, snd_pcm_runtime_t *runtime, struct urb *u);
        int (*prepare_sync)(snd_usb_substream_t *subs, snd_pcm_runtime_t *runtime, struct urb *u);
        int (*retire_sync)(snd_usb_substream_t *subs, snd_pcm_runtime_t *runtime, struct urb *u);
};

struct snd_usb_substream {
        snd_usb_stream_t *stream;
        struct usb_device *dev;
        snd_pcm_substream_t *pcm_substream;
        int direction;  /* playback or capture */
        int interface;  /* current interface */
        int endpoint;   /* assigned endpoint */
        struct audioformat *cur_audiofmt;       /* current audioformat pointer (for hw_params callback) */
        unsigned int cur_rate;          /* current rate (for hw_params callback) */
        unsigned int period_bytes;      /* current period bytes (for hw_params callback) */
        unsigned int format;     /* USB data format */
        unsigned int datapipe;   /* the data i/o pipe */
        unsigned int syncpipe;   /* 1 - async out or adaptive in */
        unsigned int datainterval;      /* log_2 of data packet interval */
        unsigned int syncinterval;  /* P for adaptive mode, 0 otherwise */
        unsigned int freqn;      /* nominal sampling rate in fs/fps in Q16.16 format */
        unsigned int freqm;      /* momentary sampling rate in fs/fps in Q16.16 format */
        unsigned int freqmax;    /* maximum sampling rate, used for buffer management */
        unsigned int phase;      /* phase accumulator */
        unsigned int maxpacksize;       /* max packet size in bytes */
        unsigned int maxframesize;      /* max packet size in frames */
        unsigned int curpacksize;       /* current packet size in bytes (for capture) */
        unsigned int curframesize;      /* current packet size in frames (for capture) */
        unsigned int fill_max: 1;       /* fill max packet size always */
        unsigned int fmt_type;          /* USB audio format type (1-3) */
        unsigned int packs_per_ms;      /* packets per millisecond (for playback) */

        unsigned int running: 1;        /* running status */

        unsigned int hwptr_done;                        /* processed frame position in the buffer */
        unsigned int transfer_done;             /* processed frames since last period update */
        unsigned long active_mask;      /* bitmask of active urbs */
        unsigned long unlink_mask;      /* bitmask of unlinked urbs */

        unsigned int nurbs;                     /* # urbs */
        snd_urb_ctx_t dataurb[MAX_URBS];        /* data urb table */
        snd_urb_ctx_t syncurb[SYNC_URBS];       /* sync urb table */
        char *syncbuf;                          /* sync buffer for all sync URBs */
        dma_addr_t sync_dma;                    /* DMA address of syncbuf */

        u64 formats;                    /* format bitmasks (all or'ed) */
        unsigned int num_formats;               /* number of supported audio formats (list) */
        struct list_head fmt_list;      /* format list */
        spinlock_t lock;
        struct tasklet_struct start_period_elapsed;     /* for start trigger */

        struct snd_urb_ops ops;         /* callbacks (must be filled at init) */
};


struct snd_usb_stream {
        snd_usb_audio_t *chip;
        snd_pcm_t *pcm;
        int pcm_index;
        unsigned int fmt_type;          /* USB audio format type (1-3) */
        snd_usb_substream_t substream[2];
        struct list_head list;
};


/*
 * we keep the snd_usb_audio_t instances by ourselves for merging
 * the all interfaces on the same card as one sound device.
 */

static DECLARE_MUTEX(register_mutex);
static snd_usb_audio_t *usb_chip[SNDRV_CARDS];


/*
 * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
 * this will overflow at approx 524 kHz
 */
static inline unsigned get_usb_full_speed_rate(unsigned int rate)
{
        return ((rate << 13) + 62) / 125;
}

/*
 * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
 * this will overflow at approx 4 MHz
 */
static inline unsigned get_usb_high_speed_rate(unsigned int rate)
{
        return ((rate << 10) + 62) / 125;
}

/* convert our full speed USB rate into sampling rate in Hz */
static inline unsigned get_full_speed_hz(unsigned int usb_rate)
{
        return (usb_rate * 125 + (1 << 12)) >> 13;
}

/* convert our high speed USB rate into sampling rate in Hz */
static inline unsigned get_high_speed_hz(unsigned int usb_rate)
{
        return (usb_rate * 125 + (1 << 9)) >> 10;
}


/*
 * prepare urb for full speed capture sync pipe
 *
 * fill the length and offset of each urb descriptor.
 * the fixed 10.14 frequency is passed through the pipe.
 */
static int prepare_capture_sync_urb(snd_usb_substream_t *subs,
                                    snd_pcm_runtime_t *runtime,
                                    struct urb *urb)
{
        unsigned char *cp = urb->transfer_buffer;
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 3;
        urb->iso_frame_desc[0].offset = 0;
        cp[0] = subs->freqn >> 2;
        cp[1] = subs->freqn >> 10;
        cp[2] = subs->freqn >> 18;
        return 0;
}

/*
 * prepare urb for high speed capture sync pipe
 *
 * fill the length and offset of each urb descriptor.
 * the fixed 12.13 frequency is passed as 16.16 through the pipe.
 */
static int prepare_capture_sync_urb_hs(snd_usb_substream_t *subs,
                                       snd_pcm_runtime_t *runtime,
                                       struct urb *urb)
{
        unsigned char *cp = urb->transfer_buffer;
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 4;
        urb->iso_frame_desc[0].offset = 0;
        cp[0] = subs->freqn;
        cp[1] = subs->freqn >> 8;
        cp[2] = subs->freqn >> 16;
        cp[3] = subs->freqn >> 24;
        return 0;
}

/*
 * process after capture sync complete
 * - nothing to do
 */
static int retire_capture_sync_urb(snd_usb_substream_t *subs,
                                   snd_pcm_runtime_t *runtime,
                                   struct urb *urb)
{
        return 0;
}

/*
 * prepare urb for capture data pipe
 *
 * fill the offset and length of each descriptor.
 *
 * we use a temporary buffer to write the captured data.
 * since the length of written data is determined by host, we cannot
 * write onto the pcm buffer directly...  the data is thus copied
 * later at complete callback to the global buffer.
 */
static int prepare_capture_urb(snd_usb_substream_t *subs,
                               snd_pcm_runtime_t *runtime,
                               struct urb *urb)
{
        int i, offs;
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        offs = 0;
        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        for (i = 0; i < ctx->packets; i++) {
                urb->iso_frame_desc[i].offset = offs;
                urb->iso_frame_desc[i].length = subs->curpacksize;
                offs += subs->curpacksize;
        }
        urb->transfer_buffer_length = offs;
        urb->number_of_packets = ctx->packets;
#if 0 // for check
        if (! urb->bandwidth) {
                int bustime;
                bustime = usb_check_bandwidth(urb->dev, urb);
                if (bustime < 0)
                        return bustime;
                printk("urb %d: bandwidth = %d (packets = %d)\n", ctx->index, bustime, urb->number_of_packets);
                usb_claim_bandwidth(urb->dev, urb, bustime, 1);
        }
#endif // for check
        return 0;
}

/*
 * process after capture complete
 *
 * copy the data from each desctiptor to the pcm buffer, and
 * update the current position.
 */
static int retire_capture_urb(snd_usb_substream_t *subs,
                              snd_pcm_runtime_t *runtime,
                              struct urb *urb)
{
        unsigned long flags;
        unsigned char *cp;
        int i;
        unsigned int stride, len, oldptr;
        int period_elapsed = 0;

        stride = runtime->frame_bits >> 3;

        for (i = 0; i < urb->number_of_packets; i++) {
                cp = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
                if (urb->iso_frame_desc[i].status) {
                        snd_printd(KERN_ERR "frame %d active: %d\n", i, urb->iso_frame_desc[i].status);
                        // continue;
                }
                len = urb->iso_frame_desc[i].actual_length / stride;
                if (! len)
                        continue;
                /* update the current pointer */
                spin_lock_irqsave(&subs->lock, flags);
                oldptr = subs->hwptr_done;
                subs->hwptr_done += len;
                if (subs->hwptr_done >= runtime->buffer_size)
                        subs->hwptr_done -= runtime->buffer_size;
                subs->transfer_done += len;
                if (subs->transfer_done >= runtime->period_size) {
                        subs->transfer_done -= runtime->period_size;
                        period_elapsed = 1;
                }
                spin_unlock_irqrestore(&subs->lock, flags);
                /* copy a data chunk */
                if (oldptr + len > runtime->buffer_size) {
                        unsigned int cnt = runtime->buffer_size - oldptr;
                        unsigned int blen = cnt * stride;
                        memcpy(runtime->dma_area + oldptr * stride, cp, blen);
                        memcpy(runtime->dma_area, cp + blen, len * stride - blen);
                } else {
                        memcpy(runtime->dma_area + oldptr * stride, cp, len * stride);
                }
        }
        if (period_elapsed)
                snd_pcm_period_elapsed(subs->pcm_substream);
        return 0;
}


/*
 * prepare urb for full speed playback sync pipe
 *
 * set up the offset and length to receive the current frequency.
 */

static int prepare_playback_sync_urb(snd_usb_substream_t *subs,
                                     snd_pcm_runtime_t *runtime,
                                     struct urb *urb)
{
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 3;
        urb->iso_frame_desc[0].offset = 0;
        return 0;
}

/*
 * prepare urb for high speed playback sync pipe
 *
 * set up the offset and length to receive the current frequency.
 */

static int prepare_playback_sync_urb_hs(snd_usb_substream_t *subs,
                                        snd_pcm_runtime_t *runtime,
                                        struct urb *urb)
{
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 4;
        urb->iso_frame_desc[0].offset = 0;
        return 0;
}

/*
 * process after full speed playback sync complete
 *
 * retrieve the current 10.14 frequency from pipe, and set it.
 * the value is referred in prepare_playback_urb().
 */
static int retire_playback_sync_urb(snd_usb_substream_t *subs,
                                    snd_pcm_runtime_t *runtime,
                                    struct urb *urb)
{
        unsigned int f;
        unsigned long flags;

        if (urb->iso_frame_desc[0].status == 0 &&
            urb->iso_frame_desc[0].actual_length == 3) {
                f = combine_triple((u8*)urb->transfer_buffer) << 2;
                if (f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax) {
                        spin_lock_irqsave(&subs->lock, flags);
                        subs->freqm = f;
                        spin_unlock_irqrestore(&subs->lock, flags);
                }
        }

        return 0;
}

/*
 * process after high speed playback sync complete
 *
 * retrieve the current 12.13 frequency from pipe, and set it.
 * the value is referred in prepare_playback_urb().
 */
static int retire_playback_sync_urb_hs(snd_usb_substream_t *subs,
                                       snd_pcm_runtime_t *runtime,
                                       struct urb *urb)
{
        unsigned int f;
        unsigned long flags;

        if (urb->iso_frame_desc[0].status == 0 &&
            urb->iso_frame_desc[0].actual_length == 4) {
                f = combine_quad((u8*)urb->transfer_buffer) & 0x0fffffff;
                if (f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax) {
                        spin_lock_irqsave(&subs->lock, flags);
                        subs->freqm = f;
                        spin_unlock_irqrestore(&subs->lock, flags);
                }
        }

        return 0;
}

/*
 * prepare urb for playback data pipe
 *
 * Since a URB can handle only a single linear buffer, we must use double
 * buffering when the data to be transferred overflows the buffer boundary.
 * To avoid inconsistencies when updating hwptr_done, we use double buffering
 * for all URBs.
 */
static int prepare_playback_urb(snd_usb_substream_t *subs,
                                snd_pcm_runtime_t *runtime,
                                struct urb *urb)
{
        int i, stride, offs;
        unsigned int counts;
        unsigned long flags;
        int period_elapsed = 0;
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;

        stride = runtime->frame_bits >> 3;

        offs = 0;
        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->number_of_packets = 0;
        spin_lock_irqsave(&subs->lock, flags);
        for (i = 0; i < ctx->packets; i++) {
                /* calculate the size of a packet */
                if (subs->fill_max)
                        counts = subs->maxframesize; /* fixed */
                else {
                        subs->phase = (subs->phase & 0xffff)
                                + (subs->freqm << subs->datainterval);
                        counts = subs->phase >> 16;
                        if (counts > subs->maxframesize)
                                counts = subs->maxframesize;
                }
                /* set up descriptor */
                urb->iso_frame_desc[i].offset = offs * stride;
                urb->iso_frame_desc[i].length = counts * stride;
                offs += counts;
                urb->number_of_packets++;
                subs->transfer_done += counts;
                if (subs->transfer_done >= runtime->period_size) {
                        subs->transfer_done -= runtime->period_size;
                        period_elapsed = 1;
                        if (subs->fmt_type == USB_FORMAT_TYPE_II) {
                                if (subs->transfer_done > 0) {
                                        /* FIXME: fill-max mode is not
                                         * supported yet */
                                        offs -= subs->transfer_done;
                                        counts -= subs->transfer_done;
                                        urb->iso_frame_desc[i].length =
                                                counts * stride;
                                        subs->transfer_done = 0;
                                }
                                i++;
                                if (i < ctx->packets) {
                                        /* add a transfer delimiter */
                                        urb->iso_frame_desc[i].offset =
                                                offs * stride;
                                        urb->iso_frame_desc[i].length = 0;
                                        urb->number_of_packets++;
                                }
                                break;
                        }
                }
                /* finish at the frame boundary at/after the period boundary */
                if (period_elapsed &&
                    (i & (subs->packs_per_ms - 1)) == subs->packs_per_ms - 1)
                        break;
        }
        if (subs->hwptr_done + offs > runtime->buffer_size) {
                /* err, the transferred area goes over buffer boundary. */
                unsigned int len = runtime->buffer_size - subs->hwptr_done;
                memcpy(urb->transfer_buffer,
                       runtime->dma_area + subs->hwptr_done * stride,
                       len * stride);
                memcpy(urb->transfer_buffer + len * stride,
                       runtime->dma_area,
                       (offs - len) * stride);
        } else {
                memcpy(urb->transfer_buffer,
                       runtime->dma_area + subs->hwptr_done * stride,
                       offs * stride);
        }
        subs->hwptr_done += offs;
        if (subs->hwptr_done >= runtime->buffer_size)
                subs->hwptr_done -= runtime->buffer_size;
        spin_unlock_irqrestore(&subs->lock, flags);
        urb->transfer_buffer_length = offs * stride;
        if (period_elapsed) {
                if (likely(subs->running))
                        snd_pcm_period_elapsed(subs->pcm_substream);
                else
                        tasklet_hi_schedule(&subs->start_period_elapsed);
        }
        return 0;
}

/*
 * process after playback data complete
 * - nothing to do
 */
static int retire_playback_urb(snd_usb_substream_t *subs,
                               snd_pcm_runtime_t *runtime,
                               struct urb *urb)
{
        return 0;
}

/*
 * Delay the snd_pcm_period_elapsed() call until after the start trigger
 * callback so that we're not longer in the substream's lock.
 */
static void start_period_elapsed(unsigned long data)
{
        snd_usb_substream_t *subs = (snd_usb_substream_t *)data;
        snd_pcm_period_elapsed(subs->pcm_substream);
}


/*
 */
static struct snd_urb_ops audio_urb_ops[2] = {
        {
                .prepare =      prepare_playback_urb,
                .retire =       retire_playback_urb,
                .prepare_sync = prepare_playback_sync_urb,
                .retire_sync =  retire_playback_sync_urb,
        },
        {
                .prepare =      prepare_capture_urb,
                .retire =       retire_capture_urb,
                .prepare_sync = prepare_capture_sync_urb,
                .retire_sync =  retire_capture_sync_urb,
        },
};

static struct snd_urb_ops audio_urb_ops_high_speed[2] = {
        {
                .prepare =      prepare_playback_urb,
                .retire =       retire_playback_urb,
                .prepare_sync = prepare_playback_sync_urb_hs,
                .retire_sync =  retire_playback_sync_urb_hs,
        },
        {
                .prepare =      prepare_capture_urb,
                .retire =       retire_capture_urb,
                .prepare_sync = prepare_capture_sync_urb_hs,
                .retire_sync =  retire_capture_sync_urb,
        },
};

/*
 * complete callback from data urb
 */
static void snd_complete_urb(struct urb *urb, struct pt_regs *regs)
{
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;
        snd_usb_substream_t *subs = ctx->subs;
        snd_pcm_substream_t *substream = ctx->subs->pcm_substream;
        int err = 0;

        if ((subs->running && subs->ops.retire(subs, substream->runtime, urb)) ||
            ! subs->running || /* can be stopped during retire callback */
            (err = subs->ops.prepare(subs, substream->runtime, urb)) < 0 ||
            (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
                clear_bit(ctx->index, &subs->active_mask);
                if (err < 0) {
                        snd_printd(KERN_ERR "cannot submit urb (err = %d)\n", err);
                        snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
                }
        }
}


/*
 * complete callback from sync urb
 */
static void snd_complete_sync_urb(struct urb *urb, struct pt_regs *regs)
{
        snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;
        snd_usb_substream_t *subs = ctx->subs;
        snd_pcm_substream_t *substream = ctx->subs->pcm_substream;
        int err = 0;

        if ((subs->running && subs->ops.retire_sync(subs, substream->runtime, urb)) ||
            ! subs->running || /* can be stopped during retire callback */
            (err = subs->ops.prepare_sync(subs, substream->runtime, urb)) < 0 ||
            (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
                clear_bit(ctx->index + 16, &subs->active_mask);
                if (err < 0) {
                        snd_printd(KERN_ERR "cannot submit sync urb (err = %d)\n", err);
                        snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
                }
        }
}


/*
 * unlink active urbs.
 */
static int deactivate_urbs(snd_usb_substream_t *subs, int force, int can_sleep)
{
        unsigned int i;
        int async;

        subs->running = 0;

        if (!force && subs->stream->chip->shutdown) /* to be sure... */
                return -EBADFD;

        async = !can_sleep && async_unlink;

        if (! async && in_interrupt())
                return 0;

        for (i = 0; i < subs->nurbs; i++) {
                if (test_bit(i, &subs->active_mask)) {
                        if (! test_and_set_bit(i, &subs->unlink_mask)) {
                                struct urb *u = subs->dataurb[i].urb;
                                if (async) {
                                        u->transfer_flags |= URB_ASYNC_UNLINK;
                                        usb_unlink_urb(u);
                                } else
                                        usb_kill_urb(u);
                        }
                }
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        if (test_bit(i+16, &subs->active_mask)) {
                                if (! test_and_set_bit(i+16, &subs->unlink_mask)) {
                                        struct urb *u = subs->syncurb[i].urb;
                                        if (async) {
                                                u->transfer_flags |= URB_ASYNC_UNLINK;
                                                usb_unlink_urb(u);
                                        } else
                                                usb_kill_urb(u);
                                }
                        }
                }
        }
        return 0;
}


/*
 * set up and start data/sync urbs
 */
static int start_urbs(snd_usb_substream_t *subs, snd_pcm_runtime_t *runtime)
{
        unsigned int i;
        int err;

        if (subs->stream->chip->shutdown)
                return -EBADFD;

        for (i = 0; i < subs->nurbs; i++) {
                snd_assert(subs->dataurb[i].urb, return -EINVAL);
                if (subs->ops.prepare(subs, runtime, subs->dataurb[i].urb) < 0) {
                        snd_printk(KERN_ERR "cannot prepare datapipe for urb %d\n", i);
                        goto __error;
                }
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        snd_assert(subs->syncurb[i].urb, return -EINVAL);
                        if (subs->ops.prepare_sync(subs, runtime, subs->syncurb[i].urb) < 0) {
                                snd_printk(KERN_ERR "cannot prepare syncpipe for urb %d\n", i);
                                goto __error;
                        }
                }
        }

        subs->active_mask = 0;
        subs->unlink_mask = 0;
        subs->running = 1;
        for (i = 0; i < subs->nurbs; i++) {
                if ((err = usb_submit_urb(subs->dataurb[i].urb, GFP_ATOMIC)) < 0) {
                        snd_printk(KERN_ERR "cannot submit datapipe for urb %d, err = %d\n", i, err);
                        goto __error;
                }
                set_bit(i, &subs->active_mask);
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        if ((err = usb_submit_urb(subs->syncurb[i].urb, GFP_ATOMIC)) < 0) {
                                snd_printk(KERN_ERR "cannot submit syncpipe for urb %d, err = %d\n", i, err);
                                goto __error;
                        }
                        set_bit(i + 16, &subs->active_mask);
                }
        }
        return 0;

 __error:
        // snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
        deactivate_urbs(subs, 0, 0);
        return -EPIPE;
}


/*
 *  wait until all urbs are processed.
 */
static int wait_clear_urbs(snd_usb_substream_t *subs)
{
        unsigned long end_time = jiffies + msecs_to_jiffies(1000);
        unsigned int i;
        int alive;

        do {
                alive = 0;
                for (i = 0; i < subs->nurbs; i++) {
                        if (test_bit(i, &subs->active_mask))
                                alive++;
                }
                if (subs->syncpipe) {
                        for (i = 0; i < SYNC_URBS; i++) {
                                if (test_bit(i + 16, &subs->active_mask))
                                        alive++;
                        }
                }
                if (! alive)
                        break;
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(1);
        } while (time_before(jiffies, end_time));
        if (alive)
                snd_printk(KERN_ERR "timeout: still %d active urbs..\n", alive);
        return 0;
}


/*
 * return the current pcm pointer.  just return the hwptr_done value.
 */
static snd_pcm_uframes_t snd_usb_pcm_pointer(snd_pcm_substream_t *substream)
{
        snd_usb_substream_t *subs;
        snd_pcm_uframes_t hwptr_done;
        
        subs = (snd_usb_substream_t *)substream->runtime->private_data;
        spin_lock(&subs->lock);
        hwptr_done = subs->hwptr_done;
        spin_unlock(&subs->lock);
        return hwptr_done;
}


/*
 * start/stop substream
 */
static int snd_usb_pcm_trigger(snd_pcm_substream_t *substream, int cmd)
{
        snd_usb_substream_t *subs = (snd_usb_substream_t *)substream->runtime->private_data;
        int err;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                err = start_urbs(subs, substream->runtime);
                break;
        case SNDRV_PCM_TRIGGER_STOP:
                err = deactivate_urbs(subs, 0, 0);
                break;
        default:
                err = -EINVAL;
                break;
        }
        return err < 0 ? err : 0;
}


/*
 * release a urb data
 */
static void release_urb_ctx(snd_urb_ctx_t *u)
{
        if (u->urb) {
                if (u->buffer_size)
                        usb_buffer_free(u->subs->dev, u->buffer_size,
                                        u->urb->transfer_buffer,
                                        u->urb->transfer_dma);
                usb_free_urb(u->urb);
                u->urb = NULL;
        }
}

/*
 * release a substream
 */
static void release_substream_urbs(snd_usb_substream_t *subs, int force)
{
        int i;

        /* stop urbs (to be sure) */
        deactivate_urbs(subs, force, 1);
        wait_clear_urbs(subs);

        for (i = 0; i < MAX_URBS; i++)
                release_urb_ctx(&subs->dataurb[i]);
        for (i = 0; i < SYNC_URBS; i++)
                release_urb_ctx(&subs->syncurb[i]);
        usb_buffer_free(subs->dev, SYNC_URBS * 4,
                        subs->syncbuf, subs->sync_dma);
        subs->syncbuf = NULL;
        subs->nurbs = 0;
}

/*
 * initialize a substream for plaback/capture
 */
static int init_substream_urbs(snd_usb_substream_t *subs, unsigned int period_bytes,
                               unsigned int rate, unsigned int frame_bits)
{
        unsigned int maxsize, n, i;
        int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
        unsigned int npacks[MAX_URBS], urb_packs, total_packs, packs_per_ms;

        /* calculate the frequency in 16.16 format */
        if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
                subs->freqn = get_usb_full_speed_rate(rate);
        else
                subs->freqn = get_usb_high_speed_rate(rate);
        subs->freqm = subs->freqn;
        /* calculate max. frequency */
        if (subs->maxpacksize) {
                /* whatever fits into a max. size packet */
                maxsize = subs->maxpacksize;
                subs->freqmax = (maxsize / (frame_bits >> 3))
                                << (16 - subs->datainterval);
        } else {
                /* no max. packet size: just take 25% higher than nominal */
                subs->freqmax = subs->freqn + (subs->freqn >> 2);
                maxsize = ((subs->freqmax + 0xffff) * (frame_bits >> 3))
                                >> (16 - subs->datainterval);
        }
        subs->phase = 0;

        if (subs->fill_max)
                subs->curpacksize = subs->maxpacksize;
        else
                subs->curpacksize = maxsize;

        if (snd_usb_get_speed(subs->dev) == USB_SPEED_HIGH)
                packs_per_ms = 8 >> subs->datainterval;
        else
                packs_per_ms = 1;
        subs->packs_per_ms = packs_per_ms;

        if (is_playback) {
                urb_packs = nrpacks;
                urb_packs = max(urb_packs, (unsigned int)MIN_PACKS_URB);
                urb_packs = min(urb_packs, (unsigned int)MAX_PACKS);
        } else
                urb_packs = 1;
        urb_packs *= packs_per_ms;

        /* decide how many packets to be used */
        if (is_playback) {
                unsigned int minsize;
                /* determine how small a packet can be */
                minsize = (subs->freqn >> (16 - subs->datainterval))
                          * (frame_bits >> 3);
                /* with sync from device, assume it can be 12% lower */
                if (subs->syncpipe)
                        minsize -= minsize >> 3;
                minsize = max(minsize, 1u);
                total_packs = (period_bytes + minsize - 1) / minsize;
                /* round up to multiple of packs_per_ms */
                total_packs = (total_packs + packs_per_ms - 1)
                                & ~(packs_per_ms - 1);
                /* we need at least two URBs for queueing */
                if (total_packs < 2 * MIN_PACKS_URB * packs_per_ms)
                        total_packs = 2 * MIN_PACKS_URB * packs_per_ms;
        } else {
                total_packs = MAX_URBS * urb_packs;
        }
        subs->nurbs = (total_packs + urb_packs - 1) / urb_packs;
        if (subs->nurbs > MAX_URBS) {
                /* too much... */
                subs->nurbs = MAX_URBS;
                total_packs = MAX_URBS * urb_packs;
        }
        n = total_packs;
        for (i = 0; i < subs->nurbs; i++) {
                npacks[i] = n > urb_packs ? urb_packs : n;
                n -= urb_packs;
        }
        if (subs->nurbs <= 1) {
                /* too little - we need at least two packets
                 * to ensure contiguous playback/capture
                 */
                subs->nurbs = 2;
                npacks[0] = (total_packs + 1) / 2;
                npacks[1] = total_packs - npacks[0];
        } else if (npacks[subs->nurbs-1] < MIN_PACKS_URB * packs_per_ms) {
                /* the last packet is too small.. */
                if (subs->nurbs > 2) {
                        /* merge to the first one */
                        npacks[0] += npacks[subs->nurbs - 1];
                        subs->nurbs--;
                } else {
                        /* divide to two */
                        subs->nurbs = 2;
                        npacks[0] = (total_packs + 1) / 2;
                        npacks[1] = total_packs - npacks[0];
                }
        }

        /* allocate and initialize data urbs */
        for (i = 0; i < subs->nurbs; i++) {
                snd_urb_ctx_t *u = &subs->dataurb[i];
                u->index = i;
                u->subs = subs;
                u->packets = npacks[i];
                u->buffer_size = maxsize * u->packets;
                if (subs->fmt_type == USB_FORMAT_TYPE_II)
                        u->packets++; /* for transfer delimiter */
                u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
                if (! u->urb)
                        goto out_of_memory;
                u->urb->transfer_buffer =
                        usb_buffer_alloc(subs->dev, u->buffer_size, GFP_KERNEL,
                                         &u->urb->transfer_dma);
                if (! u->urb->transfer_buffer)
                        goto out_of_memory;
                u->urb->pipe = subs->datapipe;
                u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
                u->urb->interval = 1 << subs->datainterval;
                u->urb->context = u;
                u->urb->complete = snd_usb_complete_callback(snd_complete_urb);
        }

        if (subs->syncpipe) {
                /* allocate and initialize sync urbs */
                subs->syncbuf = usb_buffer_alloc(subs->dev, SYNC_URBS * 4,
                                                 GFP_KERNEL, &subs->sync_dma);
                if (! subs->syncbuf)
                        goto out_of_memory;
                for (i = 0; i < SYNC_URBS; i++) {
                        snd_urb_ctx_t *u = &subs->syncurb[i];
                        u->index = i;
                        u->subs = subs;
                        u->packets = 1;
                        u->urb = usb_alloc_urb(1, GFP_KERNEL);
                        if (! u->urb)
                                goto out_of_memory;
                        u->urb->transfer_buffer = subs->syncbuf + i * 4;
                        u->urb->transfer_dma = subs->sync_dma + i * 4;
                        u->urb->transfer_buffer_length = 4;
                        u->urb->pipe = subs->syncpipe;
                        u->urb->transfer_flags = URB_ISO_ASAP |
                                                 URB_NO_TRANSFER_DMA_MAP;
                        u->urb->number_of_packets = 1;
                        u->urb->interval = 1 << subs->syncinterval;
                        u->urb->context = u;
                        u->urb->complete = snd_usb_complete_callback(snd_complete_sync_urb);
                }
        }
        return 0;

out_of_memory:
        release_substream_urbs(subs, 0);
        return -ENOMEM;
}


/*
 * find a matching audio format
 */
static struct audioformat *find_format(snd_usb_substream_t *subs, unsigned int format,
                                       unsigned int rate, unsigned int channels)
{
        struct list_head *p;
        struct audioformat *found = NULL;
        int cur_attr = 0, attr;

        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                if (fp->format != format || fp->channels != channels)
                        continue;
                if (rate < fp->rate_min || rate > fp->rate_max)
                        continue;
                if (! (fp->rates & SNDRV_PCM_RATE_CONTINUOUS)) {
                        unsigned int i;
                        for (i = 0; i < fp->nr_rates; i++)
                                if (fp->rate_table[i] == rate)
                                        break;
                        if (i >= fp->nr_rates)
                                continue;
                }
                attr = fp->ep_attr & EP_ATTR_MASK;
                if (! found) {
                        found = fp;
                        cur_attr = attr;
                        continue;
                }
                /* avoid async out and adaptive in if the other method
                 * supports the same format.
                 * this is a workaround for the case like
                 * M-audio audiophile USB.
                 */
                if (attr != cur_attr) {
                        if ((attr == EP_ATTR_ASYNC &&
                             subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
                            (attr == EP_ATTR_ADAPTIVE &&
                             subs->direction == SNDRV_PCM_STREAM_CAPTURE))
                                continue;
                        if ((cur_attr == EP_ATTR_ASYNC &&
                             subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
                            (cur_attr == EP_ATTR_ADAPTIVE &&
                             subs->direction == SNDRV_PCM_STREAM_CAPTURE)) {
                                found = fp;
                                cur_attr = attr;
                                continue;
                        }
                }
                /* find the format with the largest max. packet size */
                if (fp->maxpacksize > found->maxpacksize) {
                        found = fp;
                        cur_attr = attr;
                }
        }
        return found;
}


/*
 * initialize the picth control and sample rate
 */
static int init_usb_pitch(struct usb_device *dev, int iface,
                          struct usb_host_interface *alts,
                          struct audioformat *fmt)
{
        unsigned int ep;
        unsigned char data[1];
        int err;

        ep = get_endpoint(alts, 0)->bEndpointAddress;
        /* if endpoint has pitch control, enable it */
        if (fmt->attributes & EP_CS_ATTR_PITCH_CONTROL) {
                data[0] = 1;
                if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), SET_CUR,
                                           USB_TYPE_CLASS|USB_RECIP_ENDPOINT|USB_DIR_OUT,
                                           PITCH_CONTROL << 8, ep, data, 1, 1000)) < 0) {
                        snd_printk(KERN_ERR "%d:%d:%d: cannot set enable PITCH\n",
                                   dev->devnum, iface, ep);
                        return err;
                }
        }
        return 0;
}

static int init_usb_sample_rate(struct usb_device *dev, int iface,
                                struct usb_host_interface *alts,
                                struct audioformat *fmt, int rate)
{
        unsigned int ep;
        unsigned char data[3];
        int err;

        ep = get_endpoint(alts, 0)->bEndpointAddress;
        /* if endpoint has sampling rate control, set it */
        if (fmt->attributes & EP_CS_ATTR_SAMPLE_RATE) {
                int crate;
                data[0] = rate;
                data[1] = rate >> 8;
                data[2] = rate >> 16;
                if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), SET_CUR,
                                           USB_TYPE_CLASS|USB_RECIP_ENDPOINT|USB_DIR_OUT,
                                           SAMPLING_FREQ_CONTROL << 8, ep, data, 3, 1000)) < 0) {
                        snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d to ep 0x%x\n",
                                   dev->devnum, iface, fmt->altsetting, rate, ep);
                        return err;
                }
                if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), GET_CUR,
                                           USB_TYPE_CLASS|USB_RECIP_ENDPOINT|USB_DIR_IN,
                                           SAMPLING_FREQ_CONTROL << 8, ep, data, 3, 1000)) < 0) {
                        snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq at ep 0x%x\n",
                                   dev->devnum, iface, fmt->altsetting, ep);
                        return 0; /* some devices don't support reading */
                }
                crate = data[0] | (data[1] << 8) | (data[2] << 16);
                if (crate != rate) {
                        snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);
                        // runtime->rate = crate;
                }
        }
        return 0;
}

/*
 * find a matching format and set up the interface
 */
static int set_format(snd_usb_substream_t *subs, struct audioformat *fmt)
{
        struct usb_device *dev = subs->dev;
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        struct usb_interface *iface;
        unsigned int ep, attr;
        int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
        int err;

        iface = usb_ifnum_to_if(dev, fmt->iface);
        snd_assert(iface, return -EINVAL);
        alts = &iface->altsetting[fmt->altset_idx];
        altsd = get_iface_desc(alts);
        snd_assert(altsd->bAlternateSetting == fmt->altsetting, return -EINVAL);

        if (fmt == subs->cur_audiofmt)
                return 0;

        /* close the old interface */
        if (subs->interface >= 0 && subs->interface != fmt->iface) {
                usb_set_interface(subs->dev, subs->interface, 0);
                subs->interface = -1;
                subs->format = 0;
        }

        /* set interface */
        if (subs->interface != fmt->iface || subs->format != fmt->altset_idx) {
                if (usb_set_interface(dev, fmt->iface, fmt->altsetting) < 0) {
                        snd_printk(KERN_ERR "%d:%d:%d: usb_set_interface failed\n",
                                   dev->devnum, fmt->iface, fmt->altsetting);
                        return -EIO;
                }
                snd_printdd(KERN_INFO "setting usb interface %d:%d\n", fmt->iface, fmt->altsetting);
                subs->interface = fmt->iface;
                subs->format = fmt->altset_idx;
        }

        /* create a data pipe */
        ep = fmt->endpoint & USB_ENDPOINT_NUMBER_MASK;
        if (is_playback)
                subs->datapipe = usb_sndisocpipe(dev, ep);
        else
                subs->datapipe = usb_rcvisocpipe(dev, ep);
        if (snd_usb_get_speed(subs->dev) == USB_SPEED_HIGH &&
            get_endpoint(alts, 0)->bInterval >= 1 &&
            get_endpoint(alts, 0)->bInterval <= 4)
                subs->datainterval = get_endpoint(alts, 0)->bInterval - 1;
        else
                subs->datainterval = 0;
        subs->syncpipe = subs->syncinterval = 0;
        subs->maxpacksize = fmt->maxpacksize;
        subs->fill_max = 0;

        /* we need a sync pipe in async OUT or adaptive IN mode */
        /* check the number of EP, since some devices have broken
         * descriptors which fool us.  if it has only one EP,
         * assume it as adaptive-out or sync-in.
         */
        attr = fmt->ep_attr & EP_ATTR_MASK;
        if (((is_playback && attr == EP_ATTR_ASYNC) ||
             (! is_playback && attr == EP_ATTR_ADAPTIVE)) &&
            altsd->bNumEndpoints >= 2) {
                /* check sync-pipe endpoint */
                /* ... and check descriptor size before accessing bSynchAddress
                   because there is a version of the SB Audigy 2 NX firmware lacking
                   the audio fields in the endpoint descriptors */
                if ((get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != 0x01 ||
                    (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
                     get_endpoint(alts, 1)->bSynchAddress != 0)) {
                        snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
                                   dev->devnum, fmt->iface, fmt->altsetting);
                        return -EINVAL;
                }
                ep = get_endpoint(alts, 1)->bEndpointAddress;
                if (get_endpoint(alts, 0)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
                    (( is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress | USB_DIR_IN)) ||
                     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)))) {
                        snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
                                   dev->devnum, fmt->iface, fmt->altsetting);
                        return -EINVAL;
                }
                ep &= USB_ENDPOINT_NUMBER_MASK;
                if (is_playback)
                        subs->syncpipe = usb_rcvisocpipe(dev, ep);
                else
                        subs->syncpipe = usb_sndisocpipe(dev, ep);
                if (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
                    get_endpoint(alts, 1)->bRefresh >= 1 &&
                    get_endpoint(alts, 1)->bRefresh <= 9)
                        subs->syncinterval = get_endpoint(alts, 1)->bRefresh;
                else if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
                        subs->syncinterval = 1;
                else if (get_endpoint(alts, 1)->bInterval >= 1 &&
                         get_endpoint(alts, 1)->bInterval <= 16)
                        subs->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
                else
                        subs->syncinterval = 3;
        }

        /* always fill max packet size */
        if (fmt->attributes & EP_CS_ATTR_FILL_MAX)
                subs->fill_max = 1;

        if ((err = init_usb_pitch(dev, subs->interface, alts, fmt)) < 0)
                return err;

        subs->cur_audiofmt = fmt;

#if 0
        printk("setting done: format = %d, rate = %d, channels = %d\n",
               fmt->format, fmt->rate, fmt->channels);
        printk("  datapipe = 0x%0x, syncpipe = 0x%0x\n",
               subs->datapipe, subs->syncpipe);
#endif

        return 0;
}

/*
 * hw_params callback
 *
 * allocate a buffer and set the given audio format.
 *
 * so far we use a physically linear buffer although packetize transfer
 * doesn't need a continuous area.
 * if sg buffer is supported on the later version of alsa, we'll follow
 * that.
 */
static int snd_usb_hw_params(snd_pcm_substream_t *substream,
                             snd_pcm_hw_params_t *hw_params)
{
        snd_usb_substream_t *subs = (snd_usb_substream_t *)substream->runtime->private_data;
        struct audioformat *fmt;
        unsigned int channels, rate, format;
        int ret, changed;

        ret = snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params));
        if (ret < 0)
                return ret;

        format = params_format(hw_params);
        rate = params_rate(hw_params);
        channels = params_channels(hw_params);
        fmt = find_format(subs, format, rate, channels);
        if (! fmt) {
                snd_printd(KERN_DEBUG "cannot set format: format = %s, rate = %d, channels = %d\n",
                           snd_pcm_format_name(format), rate, channels);
                return -EINVAL;
        }

        changed = subs->cur_audiofmt != fmt ||
                subs->period_bytes != params_period_bytes(hw_params) ||
                subs->cur_rate != rate;
        if ((ret = set_format(subs, fmt)) < 0)
                return ret;

        if (subs->cur_rate != rate) {
                struct usb_host_interface *alts;
                struct usb_interface *iface;
                iface = usb_ifnum_to_if(subs->dev, fmt->iface);
                alts = &iface->altsetting[fmt->altset_idx];
                ret = init_usb_sample_rate(subs->dev, subs->interface, alts, fmt, rate);
                if (ret < 0)
                        return ret;
                subs->cur_rate = rate;
        }

        if (changed) {
                /* format changed */
                release_substream_urbs(subs, 0);
                /* influenced: period_bytes, channels, rate, format, */
                ret = init_substream_urbs(subs, params_period_bytes(hw_params),
                                          params_rate(hw_params),
                                          snd_pcm_format_physical_width(params_format(hw_params)) * params_channels(hw_params));
        }

        return ret;
}

/*
 * hw_free callback
 *
 * reset the audio format and release the buffer
 */
static int snd_usb_hw_free(snd_pcm_substream_t *substream)
{
        snd_usb_substream_t *subs = (snd_usb_substream_t *)substream->runtime->private_data;

        subs->cur_audiofmt = NULL;
        subs->cur_rate = 0;
        subs->period_bytes = 0;
        release_substream_urbs(subs, 0);
        return snd_pcm_lib_free_pages(substream);
}

/*
 * prepare callback
 *
 * only a few subtle things...
 */
static int snd_usb_pcm_prepare(snd_pcm_substream_t *substream)
{
        snd_pcm_runtime_t *runtime = substream->runtime;
        snd_usb_substream_t *subs = (snd_usb_substream_t *)runtime->private_data;

        if (! subs->cur_audiofmt) {
                snd_printk(KERN_ERR "usbaudio: no format is specified!\n");
                return -ENXIO;
        }

        /* some unit conversions in runtime */
        subs->maxframesize = bytes_to_frames(runtime, subs->maxpacksize);
        subs->curframesize = bytes_to_frames(runtime, subs->curpacksize);

        /* reset the pointer */
        subs->hwptr_done = 0;
        subs->transfer_done = 0;
        subs->phase = 0;

        /* clear urbs (to be sure) */
        deactivate_urbs(subs, 0, 1);
        wait_clear_urbs(subs);

        return 0;
}

static snd_pcm_hardware_t snd_usb_playback =
{
        .info =                 (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
                                 SNDRV_PCM_INFO_BLOCK_TRANSFER |
                                 SNDRV_PCM_INFO_MMAP_VALID),
        .buffer_bytes_max =     (128*1024),
        .period_bytes_min =     64,
        .period_bytes_max =     (128*1024),
        .periods_min =          2,
        .periods_max =          1024,
};

static snd_pcm_hardware_t snd_usb_capture =
{
        .info =                 (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
                                 SNDRV_PCM_INFO_BLOCK_TRANSFER |
                                 SNDRV_PCM_INFO_MMAP_VALID),
        .buffer_bytes_max =     (128*1024),
        .period_bytes_min =     64,
        .period_bytes_max =     (128*1024),
        .periods_min =          2,
        .periods_max =          1024,
};

/*
 * h/w constraints
 */

#ifdef HW_CONST_DEBUG
#define hwc_debug(fmt, args...) printk(KERN_DEBUG fmt, ##args)
#else
#define hwc_debug(fmt, args...) /**/
#endif

static int hw_check_valid_format(snd_pcm_hw_params_t *params, struct audioformat *fp)
{
        snd_interval_t *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
        snd_interval_t *ct = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
        snd_mask_t *fmts = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);

        /* check the format */
        if (! snd_mask_test(fmts, fp->format)) {
                hwc_debug("   > check: no supported format %d\n", fp->format);
                return 0;
        }
        /* check the channels */
        if (fp->channels < ct->min || fp->channels > ct->max) {
                hwc_debug("   > check: no valid channels %d (%d/%d)\n", fp->channels, ct->min, ct->max);
                return 0;
        }
        /* check the rate is within the range */
        if (fp->rate_min > it->max || (fp->rate_min == it->max && it->openmax)) {
                hwc_debug("   > check: rate_min %d > max %d\n", fp->rate_min, it->max);
                return 0;
        }
        if (fp->rate_max < it->min || (fp->rate_max == it->min && it->openmin)) {
                hwc_debug("   > check: rate_max %d < min %d\n", fp->rate_max, it->min);
                return 0;
        }
        return 1;
}

static int hw_rule_rate(snd_pcm_hw_params_t *params,
                        snd_pcm_hw_rule_t *rule)
{
        snd_usb_substream_t *subs = rule->private;
        struct list_head *p;
        snd_interval_t *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
        unsigned int rmin, rmax;
        int changed;

        hwc_debug("hw_rule_rate: (%d,%d)\n", it->min, it->max);
        changed = 0;
        rmin = rmax = 0;
        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                if (! hw_check_valid_format(params, fp))
                        continue;
                if (changed++) {
                        if (rmin > fp->rate_min)
                                rmin = fp->rate_min;
                        if (rmax < fp->rate_max)
                                rmax = fp->rate_max;
                } else {
                        rmin = fp->rate_min;
                        rmax = fp->rate_max;
                }
        }

        if (! changed) {
                hwc_debug("  --> get empty\n");
                it->empty = 1;
                return -EINVAL;
        }

        changed = 0;
        if (it->min < rmin) {
                it->min = rmin;
                it->openmin = 0;
                changed = 1;
        }
        if (it->max > rmax) {
                it->max = rmax;
                it->openmax = 0;
                changed = 1;
        }
        if (snd_interval_checkempty(it)) {
                it->empty = 1;
                return -EINVAL;
        }
        hwc_debug("  --> (%d, %d) (changed = %d)\n", it->min, it->max, changed);
        return changed;
}


static int hw_rule_channels(snd_pcm_hw_params_t *params,
                            snd_pcm_hw_rule_t *rule)
{
        snd_usb_substream_t *subs = rule->private;
        struct list_head *p;
        snd_interval_t *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
        unsigned int rmin, rmax;
        int changed;

        hwc_debug("hw_rule_channels: (%d,%d)\n", it->min, it->max);
        changed = 0;
        rmin = rmax = 0;
        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                if (! hw_check_valid_format(params, fp))
                        continue;
                if (changed++) {
                        if (rmin > fp->channels)
                                rmin = fp->channels;
                        if (rmax < fp->channels)
                                rmax = fp->channels;
                } else {
                        rmin = fp->channels;
                        rmax = fp->channels;
                }
        }

        if (! changed) {
                hwc_debug("  --> get empty\n");
                it->empty = 1;
                return -EINVAL;
        }

        changed = 0;
        if (it->min < rmin) {
                it->min = rmin;
                it->openmin = 0;
                changed = 1;
        }
        if (it->max > rmax) {
                it->max = rmax;
                it->openmax = 0;
                changed = 1;
        }
        if (snd_interval_checkempty(it)) {
                it->empty = 1;
                return -EINVAL;
        }
        hwc_debug("  --> (%d, %d) (changed = %d)\n", it->min, it->max, changed);
        return changed;
}

static int hw_rule_format(snd_pcm_hw_params_t *params,
                          snd_pcm_hw_rule_t *rule)
{
        snd_usb_substream_t *subs = rule->private;
        struct list_head *p;
        snd_mask_t *fmt = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
        u64 fbits;
        u32 oldbits[2];
        int changed;

        hwc_debug("hw_rule_format: %x:%x\n", fmt->bits[0], fmt->bits[1]);
        fbits = 0;
        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                if (! hw_check_valid_format(params, fp))
                        continue;
                fbits |= (1ULL << fp->format);
        }

        oldbits[0] = fmt->bits[0];
        oldbits[1] = fmt->bits[1];
        fmt->bits[0] &= (u32)fbits;
        fmt->bits[1] &= (u32)(fbits >> 32);
        if (! fmt->bits[0] && ! fmt->bits[1]) {
                hwc_debug("  --> get empty\n");
                return -EINVAL;
        }
        changed = (oldbits[0] != fmt->bits[0] || oldbits[1] != fmt->bits[1]);
        hwc_debug("  --> %x:%x (changed = %d)\n", fmt->bits[0], fmt->bits[1], changed);
        return changed;
}

#define MAX_MASK        64

/*
 * check whether the registered audio formats need special hw-constraints
 */
static int check_hw_params_convention(snd_usb_substream_t *subs)
{
        int i;
        u32 *channels;
        u32 *rates;
        u32 cmaster, rmaster;
        u32 rate_min = 0, rate_max = 0;
        struct list_head *p;
        int err = 1;

        channels = kcalloc(MAX_MASK, sizeof(u32), GFP_KERNEL);
        rates = kcalloc(MAX_MASK, sizeof(u32), GFP_KERNEL);

        list_for_each(p, &subs->fmt_list) {
                struct audioformat *f;
                f = list_entry(p, struct audioformat, list);
                /* unconventional channels? */
                if (f->channels > 32)
                        goto __out;
                /* continuous rate min/max matches? */
                if (f->rates & SNDRV_PCM_RATE_CONTINUOUS) {
                        if (rate_min && f->rate_min != rate_min)
                                goto __out;
                        if (rate_max && f->rate_max != rate_max)
                                goto __out;
                        rate_min = f->rate_min;
                        rate_max = f->rate_max;
                }
                /* combination of continuous rates and fixed rates? */
                if (rates[f->format] & SNDRV_PCM_RATE_CONTINUOUS) {
                        if (f->rates != rates[f->format])
                                goto __out;
                }
                if (f->rates & SNDRV_PCM_RATE_CONTINUOUS) {
                        if (rates[f->format] && rates[f->format] != f->rates)
                                goto __out;
                }
                channels[f->format] |= (1 << f->channels);
                rates[f->format] |= f->rates;
        }
        /* check whether channels and rates match for all formats */
        cmaster = rmaster = 0;
        for (i = 0; i < MAX_MASK; i++) {
                if (cmaster != channels[i] && cmaster && channels[i])
                        goto __out;
                if (rmaster != rates[i] && rmaster && rates[i])
                        goto __out;
                if (channels[i])
                        cmaster = channels[i];
                if (rates[i])
                        rmaster = rates[i];
        }
        /* check whether channels match for all distinct rates */
        memset(channels, 0, MAX_MASK * sizeof(u32));
        list_for_each(p, &subs->fmt_list) {
                struct audioformat *f;
                f = list_entry(p, struct audioformat, list);
                if (f->rates & SNDRV_PCM_RATE_CONTINUOUS)
                        continue;
                for (i = 0; i < 32; i++) {
                        if (f->rates & (1 << i))
                                channels[i] |= (1 << f->channels);
                }
        }
        cmaster = 0;
        for (i = 0; i < 32; i++) {
                if (cmaster != channels[i] && cmaster && channels[i])
                        goto __out;
                if (channels[i])
                        cmaster = channels[i];
        }
        err = 0;

 __out:
        kfree(channels);
        kfree(rates);
        return err;
}


/*
 * set up the runtime hardware information.
 */

static int setup_hw_info(snd_pcm_runtime_t *runtime, snd_usb_substream_t *subs)
{
        struct list_head *p;
        int err;

        runtime->hw.formats = subs->formats;

        runtime->hw.rate_min = 0x7fffffff;
        runtime->hw.rate_max = 0;
        runtime->hw.channels_min = 256;
        runtime->hw.channels_max = 0;
        runtime->hw.rates = 0;
        /* check min/max rates and channels */
        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                runtime->hw.rates |= fp->rates;
                if (runtime->hw.rate_min > fp->rate_min)
                        runtime->hw.rate_min = fp->rate_min;
                if (runtime->hw.rate_max < fp->rate_max)
                        runtime->hw.rate_max = fp->rate_max;
                if (runtime->hw.channels_min > fp->channels)
                        runtime->hw.channels_min = fp->channels;
                if (runtime->hw.channels_max < fp->channels)
                        runtime->hw.channels_max = fp->channels;
                if (fp->fmt_type == USB_FORMAT_TYPE_II && fp->frame_size > 0) {
                        /* FIXME: there might be more than one audio formats... */
                        runtime->hw.period_bytes_min = runtime->hw.period_bytes_max =
                                fp->frame_size;
                }
        }

        /* set the period time minimum 1ms */
        snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_TIME,
                                     1000 * MIN_PACKS_URB,
                                     /*(nrpacks * MAX_URBS) * 1000*/ UINT_MAX);

        if (check_hw_params_convention(subs)) {
                hwc_debug("setting extra hw constraints...\n");
                if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
                                               hw_rule_rate, subs,
                                               SNDRV_PCM_HW_PARAM_FORMAT,
                                               SNDRV_PCM_HW_PARAM_CHANNELS,
                                               -1)) < 0)
                        return err;
                if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
                                               hw_rule_channels, subs,
                                               SNDRV_PCM_HW_PARAM_FORMAT,
                                               SNDRV_PCM_HW_PARAM_RATE,
                                               -1)) < 0)
                        return err;
                if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
                                               hw_rule_format, subs,
                                               SNDRV_PCM_HW_PARAM_RATE,
                                               SNDRV_PCM_HW_PARAM_CHANNELS,
                                               -1)) < 0)
                        return err;
        }
        return 0;
}

static int snd_usb_pcm_open(snd_pcm_substream_t *substream, int direction,
                            snd_pcm_hardware_t *hw)
{
        snd_usb_stream_t *as = snd_pcm_substream_chip(substream);
        snd_pcm_runtime_t *runtime = substream->runtime;
        snd_usb_substream_t *subs = &as->substream[direction];

        subs->interface = -1;
        subs->format = 0;
        runtime->hw = *hw;
        runtime->private_data = subs;
        subs->pcm_substream = substream;
        return setup_hw_info(runtime, subs);
}

static int snd_usb_pcm_close(snd_pcm_substream_t *substream, int direction)
{
        snd_usb_stream_t *as = snd_pcm_substream_chip(substream);
        snd_usb_substream_t *subs = &as->substream[direction];

        if (subs->interface >= 0) {
                usb_set_interface(subs->dev, subs->interface, 0);
                subs->interface = -1;
        }
        subs->pcm_substream = NULL;
        return 0;
}

static int snd_usb_playback_open(snd_pcm_substream_t *substream)
{
        return snd_usb_pcm_open(substream, SNDRV_PCM_STREAM_PLAYBACK, &snd_usb_playback);
}

static int snd_usb_playback_close(snd_pcm_substream_t *substream)
{
        return snd_usb_pcm_close(substream, SNDRV_PCM_STREAM_PLAYBACK);
}

static int snd_usb_capture_open(snd_pcm_substream_t *substream)
{
        return snd_usb_pcm_open(substream, SNDRV_PCM_STREAM_CAPTURE, &snd_usb_capture);
}

static int snd_usb_capture_close(snd_pcm_substream_t *substream)
{
        return snd_usb_pcm_close(substream, SNDRV_PCM_STREAM_CAPTURE);
}

static snd_pcm_ops_t snd_usb_playback_ops = {
        .open =         snd_usb_playback_open,
        .close =        snd_usb_playback_close,
        .ioctl =        snd_pcm_lib_ioctl,
        .hw_params =    snd_usb_hw_params,
        .hw_free =      snd_usb_hw_free,
        .prepare =      snd_usb_pcm_prepare,
        .trigger =      snd_usb_pcm_trigger,
        .pointer =      snd_usb_pcm_pointer,
};

static snd_pcm_ops_t snd_usb_capture_ops = {
        .open =         snd_usb_capture_open,
        .close =        snd_usb_capture_close,
        .ioctl =        snd_pcm_lib_ioctl,
        .hw_params =    snd_usb_hw_params,
        .hw_free =      snd_usb_hw_free,
        .prepare =      snd_usb_pcm_prepare,
        .trigger =      snd_usb_pcm_trigger,
        .pointer =      snd_usb_pcm_pointer,
};



/*
 * helper functions
 */

/*
 * combine bytes and get an integer value
 */
unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
{
        switch (size) {
        case 1:  return *bytes;
        case 2:  return combine_word(bytes);
        case 3:  return combine_triple(bytes);
        case 4:  return combine_quad(bytes);
        default: return 0;
        }
}

/*
 * parse descriptor buffer and return the pointer starting the given
 * descriptor type.
 */
void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
{
        u8 *p, *end, *next;

        p = descstart;
        end = p + desclen;
        for (; p < end;) {
                if (p[0] < 2)
                        return NULL;
                next = p + p[0];
                if (next > end)
                        return NULL;
                if (p[1] == dtype && (!after || (void *)p > after)) {
                        return p;
                }
                p = next;
        }
        return NULL;
}

/*
 * find a class-specified interface descriptor with the given subtype.
 */
void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
{
        unsigned char *p = after;

        while ((p = snd_usb_find_desc(buffer, buflen, p,
                                      USB_DT_CS_INTERFACE)) != NULL) {
                if (p[0] >= 3 && p[2] == dsubtype)
                        return p;
        }
        return NULL;
}

/*
 * Wrapper for usb_control_msg().
 * Allocates a temp buffer to prevent dmaing from/to the stack.
 */
int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
                    __u8 requesttype, __u16 value, __u16 index, void *data,
                    __u16 size, int timeout)
{
        int err;
        void *buf = NULL;

        if (size > 0) {
                buf = kmalloc(size, GFP_KERNEL);
                if (!buf)
                        return -ENOMEM;
                memcpy(buf, data, size);
        }
        err = usb_control_msg(dev, pipe, request, requesttype,
                              value, index, buf, size, timeout);
        if (size > 0) {
                memcpy(data, buf, size);
                kfree(buf);
        }
        return err;
}


/*
 * entry point for linux usb interface
 */

static int usb_audio_probe(struct usb_interface *intf,
                           const struct usb_device_id *id);
static void usb_audio_disconnect(struct usb_interface *intf);

static struct usb_device_id usb_audio_ids [] = {
#include "usbquirks.h"
    { .match_flags = (USB_DEVICE_ID_MATCH_INT_CLASS | USB_DEVICE_ID_MATCH_INT_SUBCLASS),
      .bInterfaceClass = USB_CLASS_AUDIO,
      .bInterfaceSubClass = USB_SUBCLASS_AUDIO_CONTROL },
    { }                                         /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, usb_audio_ids);

static struct usb_driver usb_audio_driver = {
        .owner =        THIS_MODULE,
        .name =         "snd-usb-audio",
        .probe =        usb_audio_probe,
        .disconnect =   usb_audio_disconnect,
        .id_table =     usb_audio_ids,
};


/*
 * proc interface for list the supported pcm formats
 */
static void proc_dump_substream_formats(snd_usb_substream_t *subs, snd_info_buffer_t *buffer)
{
        struct list_head *p;
        static char *sync_types[4] = {
                "NONE", "ASYNC", "ADAPTIVE", "SYNC"
        };

        list_for_each(p, &subs->fmt_list) {
                struct audioformat *fp;
                fp = list_entry(p, struct audioformat, list);
                snd_iprintf(buffer, "  Interface %d\n", fp->iface);
                snd_iprintf(buffer, "    Altset %d\n", fp->altsetting);
                snd_iprintf(buffer, "    Format: %s\n", snd_pcm_format_name(fp->format));
                snd_iprintf(buffer, "    Channels: %d\n", fp->channels);
                snd_iprintf(buffer, "    Endpoint: %d %s (%s)\n",
                            fp->endpoint & USB_ENDPOINT_NUMBER_MASK,
                            fp->endpoint & USB_DIR_IN ? "IN" : "OUT",
                            sync_types[(fp->ep_attr & EP_ATTR_MASK) >> 2]);
                if (fp->rates & SNDRV_PCM_RATE_CONTINUOUS) {
                        snd_iprintf(buffer, "    Rates: %d - %d (continuous)\n",
                                    fp->rate_min, fp->rate_max);
                } else {
                        unsigned int i;
                        snd_iprintf(buffer, "    Rates: ");
                        for (i = 0; i < fp->nr_rates; i++) {
                                if (i > 0)
                                        snd_iprintf(buffer, ", ");
                                snd_iprintf(buffer, "%d", fp->rate_table[i]);
                        }
                        snd_iprintf(buffer, "\n");
                }
                // snd_iprintf(buffer, "    Max Packet Size = %d\n", fp->maxpacksize);
                // snd_iprintf(buffer, "    EP Attribute = 0x%x\n", fp->attributes);
        }
}

static void proc_dump_substream_status(snd_usb_substream_t *subs, snd_info_buffer_t *buffer)
{
        if (subs->running) {
                unsigned int i;
                snd_iprintf(buffer, "  Status: Running\n");
                snd_iprintf(buffer, "    Interface = %d\n", subs->interface);
                snd_iprintf(buffer, "    Altset = %d\n", subs->format);
                snd_iprintf(buffer, "    URBs = %d [ ", subs->nurbs);
                for (i = 0; i < subs->nurbs; i++)
                        snd_iprintf(buffer, "%d ", subs->dataurb[i].packets);
                snd_iprintf(buffer, "]\n");
                snd_iprintf(buffer, "    Packet Size = %d\n", subs->curpacksize);
                snd_iprintf(buffer, "    Momentary freq = %u Hz (%#x.%04x)\n",
                            snd_usb_get_speed(subs->dev) == USB_SPEED_FULL
                            ? get_full_speed_hz(subs->freqm)
                            : get_high_speed_hz(subs->freqm),
                            subs->freqm >> 16, subs->freqm & 0xffff);
        } else {
                snd_iprintf(buffer, "  Status: Stop\n");
        }
}

static void proc_pcm_format_read(snd_info_entry_t *entry, snd_info_buffer_t *buffer)
{
        snd_usb_stream_t *stream = entry->private_data;

        snd_iprintf(buffer, "%s : %s\n", stream->chip->card->longname, stream->pcm->name);

        if (stream->substream[SNDRV_PCM_STREAM_PLAYBACK].num_formats) {
                snd_iprintf(buffer, "\nPlayback:\n");
                proc_dump_substream_status(&stream->substream[SNDRV_PCM_STREAM_PLAYBACK], buffer);
                proc_dump_substream_formats(&stream->substream[SNDRV_PCM_STREAM_PLAYBACK], buffer);
        }
        if (stream->substream[SNDRV_PCM_STREAM_CAPTURE].num_formats) {
                snd_iprintf(buffer, "\nCapture:\n");
                proc_dump_substream_status(&stream->substream[SNDRV_PCM_STREAM_CAPTURE], buffer);
                proc_dump_substream_formats(&stream->substream[SNDRV_PCM_STREAM_CAPTURE], buffer);
        }
}

static void proc_pcm_format_add(snd_usb_stream_t *stream)
{
        snd_info_entry_t *entry;
        char name[32];
        snd_card_t *card = stream->chip->card;

        sprintf(name, "stream%d", stream->pcm_index);
        if (! snd_card_proc_new(card, name, &entry))
                snd_info_set_text_ops(entry, stream, 1024, proc_pcm_format_read);
}


/*
 * initialize the substream instance.
 */

static void init_substream(snd_usb_stream_t *as, int stream, struct audioformat *fp)
{
        snd_usb_substream_t *subs = &as->substream[stream];

        INIT_LIST_HEAD(&subs->fmt_list);
        spin_lock_init(&subs->lock);
        if (stream == SNDRV_PCM_STREAM_PLAYBACK)
                tasklet_init(&subs->start_period_elapsed, start_period_elapsed,
                             (unsigned long)subs);

        subs->stream = as;
        subs->direction = stream;
        subs->dev = as->chip->dev;
        if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
                subs->ops = audio_urb_ops[stream];
        else
                subs->ops = audio_urb_ops_high_speed[stream];
        snd_pcm_lib_preallocate_pages(as->pcm->streams[stream].substream,
                                      SNDRV_DMA_TYPE_CONTINUOUS,
                                      snd_dma_continuous_data(GFP_NOIO),
                                      64 * 1024, 128 * 1024);
        snd_pcm_set_ops(as->pcm, stream,
                        stream == SNDRV_PCM_STREAM_PLAYBACK ?
                        &snd_usb_playback_ops : &snd_usb_capture_ops);

        list_add_tail(&fp->list, &subs->fmt_list);
        subs->formats |= 1ULL << fp->format;
        subs->endpoint = fp->endpoint;
        subs->num_formats++;
        subs->fmt_type = fp->fmt_type;
}


/*
 * free a substream
 */
static void free_substream(snd_usb_substream_t *subs)
{
        struct list_head *p, *n;

        if (! subs->num_formats)
                return; /* not initialized */
        list_for_each_safe(p, n, &subs->fmt_list) {
                struct audioformat *fp = list_entry(p, struct audioformat, list);
                kfree(fp->rate_table);
                kfree(fp);
        }
}


/*
 * free a usb stream instance
 */
static void snd_usb_audio_stream_free(snd_usb_stream_t *stream)
{
        free_substream(&stream->substream[0]);
        free_substream(&stream->substream[1]);
        list_del(&stream->list);
        kfree(stream);
}

static void snd_usb_audio_pcm_free(snd_pcm_t *pcm)
{
        snd_usb_stream_t *stream = pcm->private_data;
        if (stream) {
                stream->pcm = NULL;
                snd_pcm_lib_preallocate_free_for_all(pcm);
                snd_usb_audio_stream_free(stream);
        }
}


/*
 * add this endpoint to the chip instance.
 * if a stream with the same endpoint already exists, append to it.
 * if not, create a new pcm stream.
 */
static int add_audio_endpoint(snd_usb_audio_t *chip, int stream, struct audioformat *fp)
{
        struct list_head *p;
        snd_usb_stream_t *as;
        snd_usb_substream_t *subs;
        snd_pcm_t *pcm;
        int err;

        list_for_each(p, &chip->pcm_list) {
                as = list_entry(p, snd_usb_stream_t, list);
                if (as->fmt_type != fp->fmt_type)
                        continue;
                subs = &as->substream[stream];
                if (! subs->endpoint)
                        continue;
                if (subs->endpoint == fp->endpoint) {
                        list_add_tail(&fp->list, &subs->fmt_list);
                        subs->num_formats++;
                        subs->formats |= 1ULL << fp->format;
                        return 0;
                }
        }
        /* look for an empty stream */
        list_for_each(p, &chip->pcm_list) {
                as = list_entry(p, snd_usb_stream_t, list);
                if (as->fmt_type != fp->fmt_type)
                        continue;
                subs = &as->substream[stream];
                if (subs->endpoint)
                        continue;
                err = snd_pcm_new_stream(as->pcm, stream, 1);
                if (err < 0)
                        return err;
                init_substream(as, stream, fp);
                return 0;
        }

        /* create a new pcm */
        as = kmalloc(sizeof(*as), GFP_KERNEL);
        if (! as)
                return -ENOMEM;
        memset(as, 0, sizeof(*as));
        as->pcm_index = chip->pcm_devs;
        as->chip = chip;
        as->fmt_type = fp->fmt_type;
        err = snd_pcm_new(chip->card, "USB Audio", chip->pcm_devs,
                          stream == SNDRV_PCM_STREAM_PLAYBACK ? 1 : 0,
                          stream == SNDRV_PCM_STREAM_PLAYBACK ? 0 : 1,
                          &pcm);
        if (err < 0) {
                kfree(as);
                return err;
        }
        as->pcm = pcm;
        pcm->private_data = as;
        pcm->private_free = snd_usb_audio_pcm_free;
        pcm->info_flags = 0;
        if (chip->pcm_devs > 0)
                sprintf(pcm->name, "USB Audio #%d", chip->pcm_devs);
        else
                strcpy(pcm->name, "USB Audio");

        init_substream(as, stream, fp);

        list_add(&as->list, &chip->pcm_list);
        chip->pcm_devs++;

        proc_pcm_format_add(as);

        return 0;
}


/*
 * check if the device uses big-endian samples
 */
static int is_big_endian_format(snd_usb_audio_t *chip, struct audioformat *fp)
{
        switch (chip->usb_id) {
        case USB_ID(0x0763, 0x2001): /* M-Audio Quattro: captured data only */
                if (fp->endpoint & USB_DIR_IN)
                        return 1;
                break;
        case USB_ID(0x0763, 0x2003): /* M-Audio Audiophile USB */
                return 1;
        }
        return 0;
}

/*
 * parse the audio format type I descriptor
 * and returns the corresponding pcm format
 *
 * @dev: usb device
 * @fp: audioformat record
 * @format: the format tag (wFormatTag)
 * @fmt: the format type descriptor
 */
static int parse_audio_format_i_type(snd_usb_audio_t *chip, struct audioformat *fp,
                                     int format, unsigned char *fmt)
{
        int pcm_format;
        int sample_width, sample_bytes;

        /* FIXME: correct endianess and sign? */
        pcm_format = -1;
        sample_width = fmt[6];
        sample_bytes = fmt[5];
        switch (format) {
        case 0: /* some devices don't define this correctly... */
                snd_printdd(KERN_INFO "%d:%u:%d : format type 0 is detected, processed as PCM\n",
                            chip->dev->devnum, fp->iface, fp->altsetting);
                /* fall-through */
        case USB_AUDIO_FORMAT_PCM:
                if (sample_width > sample_bytes * 8) {
                        snd_printk(KERN_INFO "%d:%u:%d : sample bitwidth %d in over sample bytes %d\n",
                                   chip->dev->devnum, fp->iface, fp->altsetting,
                                   sample_width, sample_bytes);
                }
                /* check the format byte size */
                switch (fmt[5]) {
                case 1:
                        pcm_format = SNDRV_PCM_FORMAT_S8;
                        break;
                case 2:
                        if (is_big_endian_format(chip, fp))
                                pcm_format = SNDRV_PCM_FORMAT_S16_BE; /* grrr, big endian!! */
                        else
                                pcm_format = SNDRV_PCM_FORMAT_S16_LE;
                        break;
                case 3:
                        if (is_big_endian_format(chip, fp))
                                pcm_format = SNDRV_PCM_FORMAT_S24_3BE; /* grrr, big endian!! */
                        else
                                pcm_format = SNDRV_PCM_FORMAT_S24_3LE;
                        break;
                case 4:
                        pcm_format = SNDRV_PCM_FORMAT_S32_LE;
                        break;
                default:
                        snd_printk(KERN_INFO "%d:%u:%d : unsupported sample bitwidth %d in %d bytes\n",
                                   chip->dev->devnum, fp->iface,
                                   fp->altsetting, sample_width, sample_bytes);
                        break;
                }
                break;
        case USB_AUDIO_FORMAT_PCM8:
                /* Dallas DS4201 workaround */
                if (chip->usb_id == USB_ID(0x04fa, 0x4201))
                        pcm_format = SNDRV_PCM_FORMAT_S8;
                else
                        pcm_format = SNDRV_PCM_FORMAT_U8;
                break;
        case USB_AUDIO_FORMAT_IEEE_FLOAT:
                pcm_format = SNDRV_PCM_FORMAT_FLOAT_LE;
                break;
        case USB_AUDIO_FORMAT_ALAW:
                pcm_format = SNDRV_PCM_FORMAT_A_LAW;
                break;
        case USB_AUDIO_FORMAT_MU_LAW:
                pcm_format = SNDRV_PCM_FORMAT_MU_LAW;
                break;
        default:
                snd_printk(KERN_INFO "%d:%u:%d : unsupported format type %d\n",
                           chip->dev->devnum, fp->iface, fp->altsetting, format);
                break;
        }
        return pcm_format;
}


/*
 * parse the format descriptor and stores the possible sample rates
 * on the audioformat table.
 *
 * @dev: usb device
 * @fp: audioformat record
 * @fmt: the format descriptor
 * @offset: the start offset of descriptor pointing the rate type
 *          (7 for type I and II, 8 for type II)
 */
static int parse_audio_format_rates(snd_usb_audio_t *chip, struct audioformat *fp,
                                    unsigned char *fmt, int offset)
{
        int nr_rates = fmt[offset];
        if (fmt[0] < offset + 1 + 3 * (nr_rates ? nr_rates : 2)) {
                snd_printk(KERN_ERR "%d:%u:%d : invalid FORMAT_TYPE desc\n",
                                   chip->dev->devnum, fp->iface, fp->altsetting);
                return -1;
        }

        if (nr_rates) {
                /*
                 * build the rate table and bitmap flags
                 */
                int r, idx, c;
                /* this table corresponds to the SNDRV_PCM_RATE_XXX bit */
                static unsigned int conv_rates[] = {
                        5512, 8000, 11025, 16000, 22050, 32000, 44100, 48000,
                        64000, 88200, 96000, 176400, 192000
                };
                fp->rate_table = kmalloc(sizeof(int) * nr_rates, GFP_KERNEL);
                if (fp->rate_table == NULL) {
                        snd_printk(KERN_ERR "cannot malloc\n");
                        return -1;
                }

                fp->nr_rates = nr_rates;
                fp->rate_min = fp->rate_max = combine_triple(&fmt[8]);
                for (r = 0, idx = offset + 1; r < nr_rates; r++, idx += 3) {
                        unsigned int rate = fp->rate_table[r] = combine_triple(&fmt[idx]);
                        if (rate < fp->rate_min)
                                fp->rate_min = rate;
                        else if (rate > fp->rate_max)
                                fp->rate_max = rate;
                        for (c = 0; c < (int)ARRAY_SIZE(conv_rates); c++) {
                                if (rate == conv_rates[c]) {
                                        fp->rates |= (1 << c);
                                        break;
                                }
                        }
                }
        } else {
                /* continuous rates */
                fp->rates = SNDRV_PCM_RATE_CONTINUOUS;
                fp->rate_min = combine_triple(&fmt[offset + 1]);
                fp->rate_max = combine_triple(&fmt[offset + 4]);
        }
        return 0;
}

/*
 * parse the format type I and III descriptors
 */
static int parse_audio_format_i(snd_usb_audio_t *chip, struct audioformat *fp,
                                int format, unsigned char *fmt)
{
        int pcm_format;

        if (fmt[3] == USB_FORMAT_TYPE_III) {
                /* FIXME: the format type is really IECxxx
                 *        but we give normal PCM format to get the existing
                 *        apps working...
                 */
                pcm_format = SNDRV_PCM_FORMAT_S16_LE;
        } else {
                pcm_format = parse_audio_format_i_type(chip, fp, format, fmt);
                if (pcm_format < 0)
                        return -1;
        }
        fp->format = pcm_format;
        fp->channels = fmt[4];
        if (fp->channels < 1) {
                snd_printk(KERN_ERR "%d:%u:%d : invalid channels %d\n",
                           chip->dev->devnum, fp->iface, fp->altsetting, fp->channels);
                return -1;
        }
        return parse_audio_format_rates(chip, fp, fmt, 7);
}

/*
 * prase the format type II descriptor
 */
static int parse_audio_format_ii(snd_usb_audio_t *chip, struct audioformat *fp,
                                 int format, unsigned char *fmt)
{
        int brate, framesize;
        switch (format) {
        case USB_AUDIO_FORMAT_AC3:
                /* FIXME: there is no AC3 format defined yet */
                // fp->format = SNDRV_PCM_FORMAT_AC3;
                fp->format = SNDRV_PCM_FORMAT_U8; /* temporarily hack to receive byte streams */
                break;
        case USB_AUDIO_FORMAT_MPEG:
                fp->format = SNDRV_PCM_FORMAT_MPEG;
                break;
        default:
                snd_printd(KERN_INFO "%d:%u:%d : unknown format tag 0x%x is detected.  processed as MPEG.\n",
                           chip->dev->devnum, fp->iface, fp->altsetting, format);
                fp->format = SNDRV_PCM_FORMAT_MPEG;
                break;
        }
        fp->channels = 1;
        brate = combine_word(&fmt[4]);  /* fmt[4,5] : wMaxBitRate (in kbps) */
        framesize = combine_word(&fmt[6]); /* fmt[6,7]: wSamplesPerFrame */
        snd_printd(KERN_INFO "found format II with max.bitrate = %d, frame size=%d\n", brate, framesize);
        fp->frame_size = framesize;
        return parse_audio_format_rates(chip, fp, fmt, 8); /* fmt[8..] sample rates */
}

static int parse_audio_format(snd_usb_audio_t *chip, struct audioformat *fp,
                              int format, unsigned char *fmt, int stream)
{
        int err;

        switch (fmt[3]) {
        case USB_FORMAT_TYPE_I:
        case USB_FORMAT_TYPE_III:
                err = parse_audio_format_i(chip, fp, format, fmt);
                break;
        case USB_FORMAT_TYPE_II:
                err = parse_audio_format_ii(chip, fp, format, fmt);
                break;
        default:
                snd_printd(KERN_INFO "%d:%u:%d : format type %d is not supported yet\n",
                           chip->dev->devnum, fp->iface, fp->altsetting, fmt[3]);
                return -1;
        }
        fp->fmt_type = fmt[3];
        if (err < 0)
                return err;
#if 1
        /* FIXME: temporary hack for extigy/audigy 2 nx */
        /* extigy apparently supports sample rates other than 48k
         * but not in ordinary way.  so we enable only 48k atm.
         */
        if (chip->usb_id == USB_ID(0x041e, 0x3000) ||
            chip->usb_id == USB_ID(0x041e, 0x3020)) {
                if (fmt[3] == USB_FORMAT_TYPE_I &&
                    fp->rates != SNDRV_PCM_RATE_48000 &&
                    fp->rates != SNDRV_PCM_RATE_96000)
                        return -1;
        }
#endif
        return 0;
}

static int parse_audio_endpoints(snd_usb_audio_t *chip, int iface_no)
{
        struct usb_device *dev;
        struct usb_interface *iface;
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        int i, altno, err, stream;
        int format;
        struct audioformat *fp;
        unsigned char *fmt, *csep;

        dev = chip->dev;

        /* parse the interface's altsettings */
        iface = usb_ifnum_to_if(dev, iface_no);
        for (i = 0; i < iface->num_altsetting; i++) {
                alts = &iface->altsetting[i];
                altsd = get_iface_desc(alts);
                /* skip invalid one */
                if ((altsd->bInterfaceClass != USB_CLASS_AUDIO &&
                     altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC) ||
                    (altsd->bInterfaceSubClass != USB_SUBCLASS_AUDIO_STREAMING &&
                     altsd->bInterfaceSubClass != USB_SUBCLASS_VENDOR_SPEC) ||
                    altsd->bNumEndpoints < 1 ||
                    le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize) == 0)
                        continue;
                /* must be isochronous */
                if ((get_endpoint(alts, 0)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) !=
                    USB_ENDPOINT_XFER_ISOC)
                        continue;
                /* check direction */
                stream = (get_endpoint(alts, 0)->bEndpointAddress & USB_DIR_IN) ?
                        SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
                altno = altsd->bAlternateSetting;

                /* get audio formats */
                fmt = snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, AS_GENERAL);
                if (!fmt) {
                        snd_printk(KERN_ERR "%d:%u:%d : AS_GENERAL descriptor not found\n",
                                   dev->devnum, iface_no, altno);
                        continue;
                }

                if (fmt[0] < 7) {
                        snd_printk(KERN_ERR "%d:%u:%d : invalid AS_GENERAL desc\n",
                                   dev->devnum, iface_no, altno);
                        continue;
                }

                format = (fmt[6] << 8) | fmt[5]; /* remember the format value */

                /* get format type */
                fmt = snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, FORMAT_TYPE);
                if (!fmt) {
                        snd_printk(KERN_ERR "%d:%u:%d : no FORMAT_TYPE desc\n",
                                   dev->devnum, iface_no, altno);
                        continue;
                }
                if (fmt[0] < 8) {
                        snd_printk(KERN_ERR "%d:%u:%d : invalid FORMAT_TYPE desc\n",
                                   dev->devnum, iface_no, altno);
                        continue;
                }

                csep = snd_usb_find_desc(alts->endpoint[0].extra, alts->endpoint[0].extralen, NULL, USB_DT_CS_ENDPOINT);
                /* Creamware Noah has this descriptor after the 2nd endpoint */
                if (!csep && altsd->bNumEndpoints >= 2)
                        csep = snd_usb_find_desc(alts->endpoint[1].extra, alts->endpoint[1].extralen, NULL, USB_DT_CS_ENDPOINT);
                if (!csep || csep[0] < 7 || csep[2] != EP_GENERAL) {
                        snd_printk(KERN_ERR "%d:%u:%d : no or invalid class specific endpoint descriptor\n",
                                   dev->devnum, iface_no, altno);
                        continue;
                }

                fp = kmalloc(sizeof(*fp), GFP_KERNEL);
                if (! fp) {
                        snd_printk(KERN_ERR "cannot malloc\n");
                        return -ENOMEM;
                }

                memset(fp, 0, sizeof(*fp));
                fp->iface = iface_no;
                fp->altsetting = altno;
                fp->altset_idx = i;
                fp->endpoint = get_endpoint(alts, 0)->bEndpointAddress;
                fp->ep_attr = get_endpoint(alts, 0)->bmAttributes;
                fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
                if (snd_usb_get_speed(dev) == USB_SPEED_HIGH)
                        fp->maxpacksize = (((fp->maxpacksize >> 11) & 3) + 1)
                                        * (fp->maxpacksize & 0x7ff);
                fp->attributes = csep[3];

                /* some quirks for attributes here */

                switch (chip->usb_id) {
                case USB_ID(0x0a92, 0x0053): /* AudioTrak Optoplay */
                        /* Optoplay sets the sample rate attribute although
                         * it seems not supporting it in fact.
                         */
                        fp->attributes &= ~EP_CS_ATTR_SAMPLE_RATE;
                        break;
                case USB_ID(0x041e, 0x3020): /* Creative SB Audigy 2 NX */
                case USB_ID(0x0763, 0x2003): /* M-Audio Audiophile USB */
                        /* doesn't set the sample rate attribute, but supports it */
                        fp->attributes |= EP_CS_ATTR_SAMPLE_RATE;
                        break;
                case USB_ID(0x047f, 0x0ca1): /* plantronics headset */
                case USB_ID(0x077d, 0x07af): /* Griffin iMic (note that there is
                                                an older model 77d:223) */
                /*
                 * plantronics headset and Griffin iMic have set adaptive-in
                 * although it's really not...
                 */
                        fp->ep_attr &= ~EP_ATTR_MASK;
                        if (stream == SNDRV_PCM_STREAM_PLAYBACK)
                                fp->ep_attr |= EP_ATTR_ADAPTIVE;
                        else
                                fp->ep_attr |= EP_ATTR_SYNC;
                        break;
                }

                /* ok, let's parse further... */
                if (parse_audio_format(chip, fp, format, fmt, stream) < 0) {
                        kfree(fp->rate_table);
                        kfree(fp);
                        continue;
                }

                snd_printdd(KERN_INFO "%d:%u:%d: add audio endpoint 0x%x\n", dev->devnum, iface_no, i, fp->endpoint);
                err = add_audio_endpoint(chip, stream, fp);
                if (err < 0) {
                        kfree(fp->rate_table);
                        kfree(fp);
                        return err;
                }
                /* try to set the interface... */
                usb_set_interface(chip->dev, iface_no, altno);
                init_usb_pitch(chip->dev, iface_no, alts, fp);
                init_usb_sample_rate(chip->dev, iface_no, alts, fp, fp->rate_max);
        }
        return 0;
}


/*
 * disconnect streams
 * called from snd_usb_audio_disconnect()
 */
static void snd_usb_stream_disconnect(struct list_head *head)
{
        int idx;
        snd_usb_stream_t *as;
        snd_usb_substream_t *subs;

        as = list_entry(head, snd_usb_stream_t, list);
        for (idx = 0; idx < 2; idx++) {
                subs = &as->substream[idx];
                if (!subs->num_formats)
                        return;
                release_substream_urbs(subs, 1);
                subs->interface = -1;
        }
}

/*
 * parse audio control descriptor and create pcm/midi streams
 */
static int snd_usb_create_streams(snd_usb_audio_t *chip, int ctrlif)
{
        struct usb_device *dev = chip->dev;
        struct usb_host_interface *host_iface;
        struct usb_interface *iface;
        unsigned char *p1;
        int i, j;

        /* find audiocontrol interface */
        host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
        if (!(p1 = snd_usb_find_csint_desc(host_iface->extra, host_iface->extralen, NULL, HEADER))) {
                snd_printk(KERN_ERR "cannot find HEADER\n");
                return -EINVAL;
        }
        if (! p1[7] || p1[0] < 8 + p1[7]) {
                snd_printk(KERN_ERR "invalid HEADER\n");
                return -EINVAL;
        }

        /*
         * parse all USB audio streaming interfaces
         */
        for (i = 0; i < p1[7]; i++) {
                struct usb_host_interface *alts;
                struct usb_interface_descriptor *altsd;
                j = p1[8 + i];
                iface = usb_ifnum_to_if(dev, j);
                if (!iface) {
                        snd_printk(KERN_ERR "%d:%u:%d : does not exist\n",
                                   dev->devnum, ctrlif, j);
                        continue;
                }
                if (usb_interface_claimed(iface)) {
                        snd_printdd(KERN_INFO "%d:%d:%d: skipping, already claimed\n", dev->devnum, ctrlif, j);
                        continue;
                }
                alts = &iface->altsetting[0];
                altsd = get_iface_desc(alts);
                if ((altsd->bInterfaceClass == USB_CLASS_AUDIO ||
                     altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC) &&
                    altsd->bInterfaceSubClass == USB_SUBCLASS_MIDI_STREAMING) {
                        if (snd_usb_create_midi_interface(chip, iface, NULL) < 0) {
                                snd_printk(KERN_ERR "%d:%u:%d: cannot create sequencer device\n", dev->devnum, ctrlif, j);
                                continue;
                        }
                        usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
                        continue;
                }
                if ((altsd->bInterfaceClass != USB_CLASS_AUDIO &&
                     altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC) ||
                    altsd->bInterfaceSubClass != USB_SUBCLASS_AUDIO_STREAMING) {
                        snd_printdd(KERN_ERR "%d:%u:%d: skipping non-supported interface %d\n", dev->devnum, ctrlif, j, altsd->bInterfaceClass);
                        /* skip non-supported classes */
                        continue;
                }
                if (! parse_audio_endpoints(chip, j)) {
                        usb_set_interface(dev, j, 0); /* reset the current interface */
                        usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
                }
        }

        return 0;
}

/*
 * create a stream for an endpoint/altsetting without proper descriptors
 */
static int create_fixed_stream_quirk(snd_usb_audio_t *chip,
                                     struct usb_interface *iface,
                                     const snd_usb_audio_quirk_t *quirk)
{
        struct audioformat *fp;
        struct usb_host_interface *alts;
        int stream, err;
        int *rate_table = NULL;

        fp = kmalloc(sizeof(*fp), GFP_KERNEL);
        if (! fp) {
                snd_printk(KERN_ERR "cannot malloc\n");
                return -ENOMEM;
        }
        memcpy(fp, quirk->data, sizeof(*fp));
        if (fp->nr_rates > 0) {
                rate_table = kmalloc(sizeof(int) * fp->nr_rates, GFP_KERNEL);
                if (!rate_table) {
                        kfree(fp);
                        return -ENOMEM;
                }
                memcpy(rate_table, fp->rate_table, sizeof(int) * fp->nr_rates);
                fp->rate_table = rate_table;
        }

        stream = (fp->endpoint & USB_DIR_IN)
                ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
        err = add_audio_endpoint(chip, stream, fp);
        if (err < 0) {
                kfree(fp);
                kfree(rate_table);
                return err;
        }
        if (fp->iface != get_iface_desc(&iface->altsetting[0])->bInterfaceNumber ||
            fp->altset_idx >= iface->num_altsetting) {
                kfree(fp);
                kfree(rate_table);
                return -EINVAL;
        }
        alts = &iface->altsetting[fp->altset_idx];
        usb_set_interface(chip->dev, fp->iface, 0);
        init_usb_pitch(chip->dev, fp->iface, alts, fp);
        init_usb_sample_rate(chip->dev, fp->iface, alts, fp, fp->rate_max);
        return 0;
}

/*
 * create a stream for an interface with proper descriptors
 */
static int create_standard_interface_quirk(snd_usb_audio_t *chip,
                                           struct usb_interface *iface,
                                           const snd_usb_audio_quirk_t *quirk)
{
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        int err;

        alts = &iface->altsetting[0];
        altsd = get_iface_desc(alts);
        switch (quirk->type) {
        case QUIRK_AUDIO_STANDARD_INTERFACE:
                err = parse_audio_endpoints(chip, altsd->bInterfaceNumber);
                if (!err)
                        usb_set_interface(chip->dev, altsd->bInterfaceNumber, 0); /* reset the current interface */
                break;
        case QUIRK_MIDI_STANDARD_INTERFACE:
                err = snd_usb_create_midi_interface(chip, iface, NULL);
                break;
        default:
                snd_printd(KERN_ERR "invalid quirk type %d\n", quirk->type);
                return -ENXIO;
        }
        if (err < 0) {
                snd_printk(KERN_ERR "cannot setup if %d: error %d\n",
                           altsd->bInterfaceNumber, err);
                return err;
        }
        return 0;
}

/*
 * Create a stream for an Edirol UA-700/UA-25 interface.  The only way
 * to detect the sample rate is by looking at wMaxPacketSize.
 */
static int create_ua700_ua25_quirk(snd_usb_audio_t *chip,
                                   struct usb_interface *iface,
                                   const snd_usb_audio_quirk_t *quirk)
{
        static const struct audioformat ua_format = {
                .format = SNDRV_PCM_FORMAT_S24_3LE,
                .channels = 2,
                .fmt_type = USB_FORMAT_TYPE_I,
                .altsetting = 1,
                .altset_idx = 1,
                .rates = SNDRV_PCM_RATE_CONTINUOUS,
        };
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        struct audioformat *fp;
        int stream, err;

        /* both PCM and MIDI interfaces have 2 altsettings */
        if (iface->num_altsetting != 2)
                return -ENXIO;
        alts = &iface->altsetting[1];
        altsd = get_iface_desc(alts);

        if (altsd->bNumEndpoints == 2) {
                static const snd_usb_midi_endpoint_info_t ua700_ep = {
                        .out_cables = 0x0003,
                        .in_cables  = 0x0003
                };
                static const snd_usb_audio_quirk_t ua700_quirk = {
                        .type = QUIRK_MIDI_FIXED_ENDPOINT,
                        .data = &ua700_ep
                };
                static const snd_usb_midi_endpoint_info_t ua25_ep = {
                        .out_cables = 0x0001,
                        .in_cables  = 0x0001
                };
                static const snd_usb_audio_quirk_t ua25_quirk = {
                        .type = QUIRK_MIDI_FIXED_ENDPOINT,
                        .data = &ua25_ep
                };
                if (chip->usb_id == USB_ID(0x0582, 0x002b))
                        return snd_usb_create_midi_interface(chip, iface,
                                                             &ua700_quirk);
                else
                        return snd_usb_create_midi_interface(chip, iface,
                                                             &ua25_quirk);
        }

        if (altsd->bNumEndpoints != 1)
                return -ENXIO;

        fp = kmalloc(sizeof(*fp), GFP_KERNEL);
        if (!fp)
                return -ENOMEM;
        memcpy(fp, &ua_format, sizeof(*fp));

        fp->iface = altsd->bInterfaceNumber;
        fp->endpoint = get_endpoint(alts, 0)->bEndpointAddress;
        fp->ep_attr = get_endpoint(alts, 0)->bmAttributes;
        fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);

        switch (fp->maxpacksize) {
        case 0x120:
                fp->rate_max = fp->rate_min = 44100;
                break;
        case 0x138:
        case 0x140:
                fp->rate_max = fp->rate_min = 48000;
                break;
        case 0x258:
        case 0x260:
                fp->rate_max = fp->rate_min = 96000;
                break;
        default:
                snd_printk(KERN_ERR "unknown sample rate\n");
                kfree(fp);
                return -ENXIO;
        }

        stream = (fp->endpoint & USB_DIR_IN)
                ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
        err = add_audio_endpoint(chip, stream, fp);
        if (err < 0) {
                kfree(fp);
                return err;
        }
        usb_set_interface(chip->dev, fp->iface, 0);
        return 0;
}

/*
 * Create a stream for an Edirol UA-1000 interface.
 */
static int create_ua1000_quirk(snd_usb_audio_t *chip,
                               struct usb_interface *iface,
                               const snd_usb_audio_quirk_t *quirk)
{
        static const struct audioformat ua1000_format = {
                .format = SNDRV_PCM_FORMAT_S32_LE,
                .fmt_type = USB_FORMAT_TYPE_I,
                .altsetting = 1,
                .altset_idx = 1,
                .attributes = 0,
                .rates = SNDRV_PCM_RATE_CONTINUOUS,
        };
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        struct audioformat *fp;
        int stream, err;

        if (iface->num_altsetting != 2)
                return -ENXIO;
        alts = &iface->altsetting[1];
        altsd = get_iface_desc(alts);
        if (alts->extralen != 11 || alts->extra[1] != CS_AUDIO_INTERFACE ||
            altsd->bNumEndpoints != 1)
                return -ENXIO;

        fp = kmalloc(sizeof(*fp), GFP_KERNEL);
        if (!fp)
                return -ENOMEM;
        memcpy(fp, &ua1000_format, sizeof(*fp));

        fp->channels = alts->extra[4];
        fp->iface = altsd->bInterfaceNumber;
        fp->endpoint = get_endpoint(alts, 0)->bEndpointAddress;
        fp->ep_attr = get_endpoint(alts, 0)->bmAttributes;
        fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
        fp->rate_max = fp->rate_min = combine_triple(&alts->extra[8]);

        stream = (fp->endpoint & USB_DIR_IN)
                ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
        err = add_audio_endpoint(chip, stream, fp);
        if (err < 0) {
                kfree(fp);
                return err;
        }
        /* FIXME: playback must be synchronized to capture */
        usb_set_interface(chip->dev, fp->iface, 0);
        return 0;
}

static int snd_usb_create_quirk(snd_usb_audio_t *chip,
                                struct usb_interface *iface,
                                const snd_usb_audio_quirk_t *quirk);

/*
 * handle the quirks for the contained interfaces
 */
static int create_composite_quirk(snd_usb_audio_t *chip,
                                  struct usb_interface *iface,
                                  const snd_usb_audio_quirk_t *quirk)
{
        int probed_ifnum = get_iface_desc(iface->altsetting)->bInterfaceNumber;
        int err;

        for (quirk = quirk->data; quirk->ifnum >= 0; ++quirk) {
                iface = usb_ifnum_to_if(chip->dev, quirk->ifnum);
                if (!iface)
                        continue;
                if (quirk->ifnum != probed_ifnum &&
                    usb_interface_claimed(iface))
                        continue;
                err = snd_usb_create_quirk(chip, iface, quirk);
                if (err < 0)
                        return err;
                if (quirk->ifnum != probed_ifnum)
                        usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
        }
        return 0;
}

static int ignore_interface_quirk(snd_usb_audio_t *chip,
                                  struct usb_interface *iface,
                                  const snd_usb_audio_quirk_t *quirk)
{
        return 0;
}


/*
 * boot quirks
 */

#define EXTIGY_FIRMWARE_SIZE_OLD 794
#define EXTIGY_FIRMWARE_SIZE_NEW 483

static int snd_usb_extigy_boot_quirk(struct usb_device *dev, struct usb_interface *intf)
{
        struct usb_host_config *config = dev->actconfig;
        int err;

        if (le16_to_cpu(get_cfg_desc(config)->wTotalLength) == EXTIGY_FIRMWARE_SIZE_OLD ||
            le16_to_cpu(get_cfg_desc(config)->wTotalLength) == EXTIGY_FIRMWARE_SIZE_NEW) {
                snd_printdd("sending Extigy boot sequence...\n");
                /* Send message to force it to reconnect with full interface. */
                err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev,0),
                                      0x10, 0x43, 0x0001, 0x000a, NULL, 0, 1000);
                if (err < 0) snd_printdd("error sending boot message: %d\n", err);
                err = usb_get_descriptor(dev, USB_DT_DEVICE, 0,
                                &dev->descriptor, sizeof(dev->descriptor));
                config = dev->actconfig;
                if (err < 0) snd_printdd("error usb_get_descriptor: %d\n", err);
                err = usb_reset_configuration(dev);
                if (err < 0) snd_printdd("error usb_reset_configuration: %d\n", err);
                snd_printdd("extigy_boot: new boot length = %d\n",
                            le16_to_cpu(get_cfg_desc(config)->wTotalLength));
                return -ENODEV; /* quit this anyway */
        }
        return 0;
}

static int snd_usb_audigy2nx_boot_quirk(struct usb_device *dev)
{
        u8 buf = 1;

        snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), 0x2a,
                        USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
                        0, 0, &buf, 1, 1000);
        if (buf == 0) {
                snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), 0x29,
                                USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_OTHER,
                                1, 2000, NULL, 0, 1000);
                return -ENODEV;
        }
        return 0;
}


/*
 * audio-interface quirks
 *
 * returns zero if no standard audio/MIDI parsing is needed.
 * returns a postive value if standard audio/midi interfaces are parsed
 * after this.
 * returns a negative value at error.
 */
static int snd_usb_create_quirk(snd_usb_audio_t *chip,
                                struct usb_interface *iface,
                                const snd_usb_audio_quirk_t *quirk)
{
        typedef int (*quirk_func_t)(snd_usb_audio_t *, struct usb_interface *,
                                    const snd_usb_audio_quirk_t *);
        static const quirk_func_t quirk_funcs[] = {
                [QUIRK_IGNORE_INTERFACE] = ignore_interface_quirk,
                [QUIRK_COMPOSITE] = create_composite_quirk,
                [QUIRK_MIDI_STANDARD_INTERFACE] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_FIXED_ENDPOINT] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_YAMAHA] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_MIDIMAN] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_NOVATION] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_RAW] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_EMAGIC] = snd_usb_create_midi_interface,
                [QUIRK_MIDI_MIDITECH] = snd_usb_create_midi_interface,
                [QUIRK_AUDIO_STANDARD_INTERFACE] = create_standard_interface_quirk,
                [QUIRK_AUDIO_FIXED_ENDPOINT] = create_fixed_stream_quirk,
                [QUIRK_AUDIO_EDIROL_UA700_UA25] = create_ua700_ua25_quirk,
                [QUIRK_AUDIO_EDIROL_UA1000] = create_ua1000_quirk,
        };

        if (quirk->type < QUIRK_TYPE_COUNT) {
                return quirk_funcs[quirk->type](chip, iface, quirk);
        } else {
                snd_printd(KERN_ERR "invalid quirk type %d\n", quirk->type);
                return -ENXIO;
        }
}


/*
 * common proc files to show the usb device info
 */
static void proc_audio_usbbus_read(snd_info_entry_t *entry, snd_info_buffer_t *buffer)
{
        snd_usb_audio_t *chip = entry->private_data;
        if (! chip->shutdown)
                snd_iprintf(buffer, "%03d/%03d\n", chip->dev->bus->busnum, chip->dev->devnum);
}

static void proc_audio_usbid_read(snd_info_entry_t *entry, snd_info_buffer_t *buffer)
{
        snd_usb_audio_t *chip = entry->private_data;
        if (! chip->shutdown)
                snd_iprintf(buffer, "%04x:%04x\n", 
                            USB_ID_VENDOR(chip->usb_id),
                            USB_ID_PRODUCT(chip->usb_id));
}

static void snd_usb_audio_create_proc(snd_usb_audio_t *chip)
{
        snd_info_entry_t *entry;
        if (! snd_card_proc_new(chip->card, "usbbus", &entry))
                snd_info_set_text_ops(entry, chip, 1024, proc_audio_usbbus_read);
        if (! snd_card_proc_new(chip->card, "usbid", &entry))
                snd_info_set_text_ops(entry, chip, 1024, proc_audio_usbid_read);
}

/*
 * free the chip instance
 *
 * here we have to do not much, since pcm and controls are already freed
 *
 */

static int snd_usb_audio_free(snd_usb_audio_t *chip)
{
        kfree(chip);
        return 0;
}

static int snd_usb_audio_dev_free(snd_device_t *device)
{
        snd_usb_audio_t *chip = device->device_data;
        return snd_usb_audio_free(chip);
}


/*
 * create a chip instance and set its names.
 */
static int snd_usb_audio_create(struct usb_device *dev, int idx,
                                const snd_usb_audio_quirk_t *quirk,
                                snd_usb_audio_t **rchip)
{
        snd_card_t *card;
        snd_usb_audio_t *chip;
        int err, len;
        char component[14];
        static snd_device_ops_t ops = {
                .dev_free =     snd_usb_audio_dev_free,
        };

        *rchip = NULL;

        if (snd_usb_get_speed(dev) != USB_SPEED_FULL &&
            snd_usb_get_speed(dev) != USB_SPEED_HIGH) {
                snd_printk(KERN_ERR "unknown device speed %d\n", snd_usb_get_speed(dev));
                return -ENXIO;
        }

        card = snd_card_new(index[idx], id[idx], THIS_MODULE, 0);
        if (card == NULL) {
                snd_printk(KERN_ERR "cannot create card instance %d\n", idx);
                return -ENOMEM;
        }

        chip = kcalloc(1, sizeof(*chip), GFP_KERNEL);
        if (! chip) {
                snd_card_free(card);
                return -ENOMEM;
        }

        chip->index = idx;
        chip->dev = dev;
        chip->card = card;
        chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
                              le16_to_cpu(dev->descriptor.idProduct));
        INIT_LIST_HEAD(&chip->pcm_list);
        INIT_LIST_HEAD(&chip->midi_list);
        INIT_LIST_HEAD(&chip->mixer_list);

        if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops)) < 0) {
                snd_usb_audio_free(chip);
                snd_card_free(card);
                return err;
        }

        strcpy(card->driver, "USB-Audio");
        sprintf(component, "USB%04x:%04x",
                USB_ID_VENDOR(chip->usb_id), USB_ID_PRODUCT(chip->usb_id));
        snd_component_add(card, component);

        /* retrieve the device string as shortname */
        if (quirk && quirk->product_name) {
                strlcpy(card->shortname, quirk->product_name, sizeof(card->shortname));
        } else {
                if (!dev->descriptor.iProduct ||
                    usb_string(dev, dev->descriptor.iProduct,
                               card->shortname, sizeof(card->shortname)) <= 0) {
                        /* no name available from anywhere, so use ID */
                        sprintf(card->shortname, "USB Device %#04x:%#04x",
                                USB_ID_VENDOR(chip->usb_id),
                                USB_ID_PRODUCT(chip->usb_id));
                }
        }

        /* retrieve the vendor and device strings as longname */
        if (quirk && quirk->vendor_name) {
                len = strlcpy(card->longname, quirk->vendor_name, sizeof(card->longname));
        } else {
                if (dev->descriptor.iManufacturer)
                        len = usb_string(dev, dev->descriptor.iManufacturer,
                                         card->longname, sizeof(card->longname));
                else
                        len = 0;
                /* we don't really care if there isn't any vendor string */
        }
        if (len > 0)
                strlcat(card->longname, " ", sizeof(card->longname));

        strlcat(card->longname, card->shortname, sizeof(card->longname));

        len = strlcat(card->longname, " at ", sizeof(card->longname));

        if (len < sizeof(card->longname))
                usb_make_path(dev, card->longname + len, sizeof(card->longname) - len);

        strlcat(card->longname,
                snd_usb_get_speed(dev) == USB_SPEED_FULL ? ", full speed" : ", high speed",
                sizeof(card->longname));

        snd_usb_audio_create_proc(chip);

        *rchip = chip;
        return 0;
}


/*
 * probe the active usb device
 *
 * note that this can be called multiple times per a device, when it
 * includes multiple audio control interfaces.
 *
 * thus we check the usb device pointer and creates the card instance
 * only at the first time.  the successive calls of this function will
 * append the pcm interface to the corresponding card.
 */
static void *snd_usb_audio_probe(struct usb_device *dev,
                                 struct usb_interface *intf,
                                 const struct usb_device_id *usb_id)
{
        struct usb_host_config *config = dev->actconfig;
        const snd_usb_audio_quirk_t *quirk = (const snd_usb_audio_quirk_t *)usb_id->driver_info;
        int i, err;
        snd_usb_audio_t *chip;
        struct usb_host_interface *alts;
        int ifnum;
        u32 id;

        alts = &intf->altsetting[0];
        ifnum = get_iface_desc(alts)->bInterfaceNumber;
        id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));

        if (quirk && quirk->ifnum >= 0 && ifnum != quirk->ifnum)
                goto __err_val;

        /* SB Extigy needs special boot-up sequence */
        /* if more models come, this will go to the quirk list. */
        if (id == USB_ID(0x041e, 0x3000)) {
                if (snd_usb_extigy_boot_quirk(dev, intf) < 0)
                        goto __err_val;
                config = dev->actconfig;
        }
        /* SB Audigy 2 NX needs its own boot-up magic, too */
        if (id == USB_ID(0x041e, 0x3020)) {
                if (snd_usb_audigy2nx_boot_quirk(dev) < 0)
                        goto __err_val;
        }

        /*
         * found a config.  now register to ALSA
         */

        /* check whether it's already registered */
        chip = NULL;
        down(&register_mutex);
        for (i = 0; i < SNDRV_CARDS; i++) {
                if (usb_chip[i] && usb_chip[i]->dev == dev) {
                        if (usb_chip[i]->shutdown) {
                                snd_printk(KERN_ERR "USB device is in the shutdown state, cannot create a card instance\n");
                                goto __error;
                        }
                        chip = usb_chip[i];
                        break;
                }
        }
        if (! chip) {
                /* it's a fresh one.
                 * now look for an empty slot and create a new card instance
                 */
                /* first, set the current configuration for this device */
                if (usb_reset_configuration(dev) < 0) {
                        snd_printk(KERN_ERR "cannot reset configuration (value 0x%x)\n", get_cfg_desc(config)->bConfigurationValue);
                        goto __error;
                }
                for (i = 0; i < SNDRV_CARDS; i++)
                        if (enable[i] && ! usb_chip[i] &&
                            (vid[i] == -1 || vid[i] == USB_ID_VENDOR(id)) &&
                            (pid[i] == -1 || pid[i] == USB_ID_PRODUCT(id))) {
                                if (snd_usb_audio_create(dev, i, quirk, &chip) < 0) {
                                        goto __error;
                                }
                                snd_card_set_dev(chip->card, &intf->dev);
                                break;
                        }
                if (! chip) {
                        snd_printk(KERN_ERR "no available usb audio device\n");
                        goto __error;
                }
        }

        err = 1; /* continue */
        if (quirk && quirk->ifnum != QUIRK_NO_INTERFACE) {
                /* need some special handlings */
                if ((err = snd_usb_create_quirk(chip, intf, quirk)) < 0)
                        goto __error;
        }

        if (err > 0) {
                /* create normal USB audio interfaces */
                if (snd_usb_create_streams(chip, ifnum) < 0 ||
                    snd_usb_create_mixer(chip, ifnum) < 0) {
                        goto __error;
                }
        }

        /* we are allowed to call snd_card_register() many times */
        if (snd_card_register(chip->card) < 0) {
                goto __error;
        }

        usb_chip[chip->index] = chip;
        chip->num_interfaces++;
        up(&register_mutex);
        return chip;

 __error:
        if (chip && !chip->num_interfaces)
                snd_card_free(chip->card);
        up(&register_mutex);
 __err_val:
        return NULL;
}

/*
 * we need to take care of counter, since disconnection can be called also
 * many times as well as usb_audio_probe().
 */
static void snd_usb_audio_disconnect(struct usb_device *dev, void *ptr)
{
        snd_usb_audio_t *chip;
        snd_card_t *card;
        struct list_head *p;

        if (ptr == (void *)-1L)
                return;

        chip = ptr;
        card = chip->card;
        down(&register_mutex);
        chip->shutdown = 1;
        chip->num_interfaces--;
        if (chip->num_interfaces <= 0) {
                snd_card_disconnect(card);
                /* release the pcm resources */
                list_for_each(p, &chip->pcm_list) {
                        snd_usb_stream_disconnect(p);
                }
                /* release the midi resources */
                list_for_each(p, &chip->midi_list) {
                        snd_usbmidi_disconnect(p);
                }
                /* release mixer resources */
                list_for_each(p, &chip->mixer_list) {
                        snd_usb_mixer_disconnect(p);
                }
                usb_chip[chip->index] = NULL;
                up(&register_mutex);
                snd_card_free(card);
        } else {
                up(&register_mutex);
        }
}

/*
 * new 2.5 USB kernel API
 */
static int usb_audio_probe(struct usb_interface *intf,
                           const struct usb_device_id *id)
{
        void *chip;
        chip = snd_usb_audio_probe(interface_to_usbdev(intf), intf, id);
        if (chip) {
                dev_set_drvdata(&intf->dev, chip);
                return 0;
        } else
                return -EIO;
}

static void usb_audio_disconnect(struct usb_interface *intf)
{
        snd_usb_audio_disconnect(interface_to_usbdev(intf),
                                 dev_get_drvdata(&intf->dev));
}


static int __init snd_usb_audio_init(void)
{
        if (nrpacks < MIN_PACKS_URB || nrpacks > MAX_PACKS) {
                printk(KERN_WARNING "invalid nrpacks value.\n");
                return -EINVAL;
        }
        usb_register(&usb_audio_driver);
        return 0;
}


static void __exit snd_usb_audio_cleanup(void)
{
        usb_deregister(&usb_audio_driver);
}

module_init(snd_usb_audio_init);
module_exit(snd_usb_audio_cleanup);