drivers/media/dvb/dvb-core/dvb_ringbuffer.h

   1 /*
   2  *
   3  * dvb_ringbuffer.h: ring buffer implementation for the dvb driver
   4  *
   5  * Copyright (C) 2003 Oliver Endriss
   6  * Copyright (C) 2004 Andrew de Quincey
   7  *
   8  * based on code originally found in av7110.c & dvb_ci.c:
   9  * Copyright (C) 1999-2003 Ralph Metzler & Marcus Metzler
  10  *                         for convergence integrated media GmbH
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public License
  14  * as published by the Free Software Foundation; either version 2.1
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25  */
  26
  27 #ifndef _DVB_RINGBUFFER_H_
  28 #define _DVB_RINGBUFFER_H_
  29
  30 #include <linux/spinlock.h>
  31 #include <linux/wait.h>
  32
  33 struct dvb_ringbuffer {
  34         u8               *data;
  35         ssize_t           size;
  36         ssize_t           pread;
  37         ssize_t           pwrite;
  38         int               error;
  39
  40         wait_queue_head_t queue;
  41         spinlock_t        lock;
  42 };
  43
  44 #define DVB_RINGBUFFER_PKTHDRSIZE 3
  45
  46
  47 /*
  48 ** Notes:
  49 ** ------
  50 ** (1) For performance reasons read and write routines don't check buffer sizes
  51 **     and/or number of bytes free/available. This has to be done before these
  52 **     routines are called. For example:
  53 **
  54 **     *** write <buflen> bytes ***
  55 **     free = dvb_ringbuffer_free(rbuf);
  56 **     if (free >= buflen)
  57 **         count = dvb_ringbuffer_write(rbuf, buffer, buflen);
  58 **     else
  59 **         ...
  60 **
  61 **     *** read min. 1000, max. <bufsize> bytes ***
  62 **     avail = dvb_ringbuffer_avail(rbuf);
  63 **     if (avail >= 1000)
  64 **         count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize), 0);
  65 **     else
  66 **         ...
  67 **
  68 ** (2) If there is exactly one reader and one writer, there is no need
  69 **     to lock read or write operations.
  70 **     Two or more readers must be locked against each other.
  71 **     Flushing the buffer counts as a read operation.
  72 **     Resetting the buffer counts as a read and write operation.
  73 **     Two or more writers must be locked against each other.
  74 */
  75
  76 /* initialize ring buffer, lock and queue */
  77 extern void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len);
  78
  79 /* test whether buffer is empty */
  80 extern int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf);
  81
  82 /* return the number of free bytes in the buffer */
  83 extern ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf);
  84
  85 /* return the number of bytes waiting in the buffer */
  86 extern ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf);
  87
  88
  89 /*
  90 ** Reset the read and write pointers to zero and flush the buffer
  91 ** This counts as a read and write operation
  92 */
  93 extern void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf);
  94
  95
  96 /* read routines & macros */
  97 /* ---------------------- */
  98 /* flush buffer */
  99 extern void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf);
 100
 101 /* flush buffer protected by spinlock and wake-up waiting task(s) */
 102 extern void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf);
 103
 104 /* peek at byte <offs> in the buffer */
 105 #define DVB_RINGBUFFER_PEEK(rbuf,offs)  \
 106                         (rbuf)->data[((rbuf)->pread+(offs))%(rbuf)->size]
 107
 108 /* advance read ptr by <num> bytes */
 109 #define DVB_RINGBUFFER_SKIP(rbuf,num)   \
 110                         (rbuf)->pread=((rbuf)->pread+(num))%(rbuf)->size
 111
 112 /*
 113 ** read <len> bytes from ring buffer into <buf>
 114 ** <usermem> specifies whether <buf> resides in user space
 115 ** returns number of bytes transferred or -EFAULT
 116 */
 117 extern ssize_t dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf,
 118                                    size_t len, int usermem);
 119
 120
 121 /* write routines & macros */
 122 /* ----------------------- */
 123 /* write single byte to ring buffer */
 124 #define DVB_RINGBUFFER_WRITE_BYTE(rbuf,byte)    \
 125                         { (rbuf)->data[(rbuf)->pwrite]=(byte); \
 126                         (rbuf)->pwrite=((rbuf)->pwrite+1)%(rbuf)->size; }
 127 /*
 128 ** write <len> bytes to ring buffer
 129 ** <usermem> specifies whether <buf> resides in user space
 130 ** returns number of bytes transferred or -EFAULT
 131 */
 132 extern ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf,
 133                                     size_t len);
 134
 135
 136 /**
 137  * Write a packet into the ringbuffer.
 138  *
 139  * <rbuf> Ringbuffer to write to.
 140  * <buf> Buffer to write.
 141  * <len> Length of buffer (currently limited to 65535 bytes max).
 142  * returns Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
 143  */
 144 extern ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf,
 145                                         size_t len);
 146
 147 /**
 148  * Read from a packet in the ringbuffer. Note: unlike dvb_ringbuffer_read(), this
 149  * does NOT update the read pointer in the ringbuffer. You must use
 150  * dvb_ringbuffer_pkt_dispose() to mark a packet as no longer required.
 151  *
 152  * <rbuf> Ringbuffer concerned.
 153  * <idx> Packet index as returned by dvb_ringbuffer_pkt_next().
 154  * <offset> Offset into packet to read from.
 155  * <buf> Destination buffer for data.
 156  * <len> Size of destination buffer.
 157  * <usermem> Set to 1 if <buf> is in userspace.
 158  * returns Number of bytes read, or -EFAULT.
 159  */
 160 extern ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
 161                                        int offset, u8* buf, size_t len, int usermem);
 162
 163 /**
 164  * Dispose of a packet in the ring buffer.
 165  *
 166  * <rbuf> Ring buffer concerned.
 167  * <idx> Packet index as returned by dvb_ringbuffer_pkt_next().
 168  */
 169 extern void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx);
 170
 171 /**
 172  * Get the index of the next packet in a ringbuffer.
 173  *
 174  * <rbuf> Ringbuffer concerned.
 175  * <idx> Previous packet index, or -1 to return the first packet index.
 176  * <pktlen> On success, will be updated to contain the length of the packet in bytes.
 177  * returns Packet index (if >=0), or -1 if no packets available.
 178  */
 179 extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen);
 180
 181
 182 #endif /* _DVB_RINGBUFFER_H_ */