[media] vb2: don't return NULL for alloc and get_userptr ops

[deliverable/linux.git] / drivers / media / v4l2-core / videobuf2-core.c

/*
 * videobuf2-core.c - video buffer 2 core framework
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <pawel@osciak.com>
 *         Marek Szyprowski <m.szyprowski@samsung.com>
 *
 * The vb2_thread implementation was based on code from videobuf-dvb.c:
 *      (c) 2004 Gerd Knorr <kraxel@bytesex.org> [SUSE Labs]
 *
 * 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.
 */

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/freezer.h>
#include <linux/kthread.h>

#include <media/videobuf2-core.h>
#include <media/v4l2-mc.h>

#include <trace/events/vb2.h>

static int debug;
module_param(debug, int, 0644);

#define dprintk(level, fmt, arg...)                                           \
        do {                                                                  \
                if (debug >= level)                                           \
                        pr_info("vb2-core: %s: " fmt, __func__, ## arg); \
        } while (0)

#ifdef CONFIG_VIDEO_ADV_DEBUG

/*
 * If advanced debugging is on, then count how often each op is called
 * successfully, which can either be per-buffer or per-queue.
 *
 * This makes it easy to check that the 'init' and 'cleanup'
 * (and variations thereof) stay balanced.
 */

#define log_memop(vb, op)                                               \
        dprintk(2, "call_memop(%p, %d, %s)%s\n",                        \
                (vb)->vb2_queue, (vb)->index, #op,                      \
                (vb)->vb2_queue->mem_ops->op ? "" : " (nop)")

#define call_memop(vb, op, args...)                                     \
({                                                                      \
        struct vb2_queue *_q = (vb)->vb2_queue;                         \
        int err;                                                        \
                                                                        \
        log_memop(vb, op);                                              \
        err = _q->mem_ops->op ? _q->mem_ops->op(args) : 0;              \
        if (!err)                                                       \
                (vb)->cnt_mem_ ## op++;                                 \
        err;                                                            \
})

#define call_ptr_memop(vb, op, args...)                                 \
({                                                                      \
        struct vb2_queue *_q = (vb)->vb2_queue;                         \
        void *ptr;                                                      \
                                                                        \
        log_memop(vb, op);                                              \
        ptr = _q->mem_ops->op ? _q->mem_ops->op(args) : NULL;           \
        if (!IS_ERR_OR_NULL(ptr))                                       \
                (vb)->cnt_mem_ ## op++;                                 \
        ptr;                                                            \
})

#define call_void_memop(vb, op, args...)                                \
({                                                                      \
        struct vb2_queue *_q = (vb)->vb2_queue;                         \
                                                                        \
        log_memop(vb, op);                                              \
        if (_q->mem_ops->op)                                            \
                _q->mem_ops->op(args);                                  \
        (vb)->cnt_mem_ ## op++;                                         \
})

#define log_qop(q, op)                                                  \
        dprintk(2, "call_qop(%p, %s)%s\n", q, #op,                      \
                (q)->ops->op ? "" : " (nop)")

#define call_qop(q, op, args...)                                        \
({                                                                      \
        int err;                                                        \
                                                                        \
        log_qop(q, op);                                                 \
        err = (q)->ops->op ? (q)->ops->op(args) : 0;                    \
        if (!err)                                                       \
                (q)->cnt_ ## op++;                                      \
        err;                                                            \
})

#define call_void_qop(q, op, args...)                                   \
({                                                                      \
        log_qop(q, op);                                                 \
        if ((q)->ops->op)                                               \
                (q)->ops->op(args);                                     \
        (q)->cnt_ ## op++;                                              \
})

#define log_vb_qop(vb, op, args...)                                     \
        dprintk(2, "call_vb_qop(%p, %d, %s)%s\n",                       \
                (vb)->vb2_queue, (vb)->index, #op,                      \
                (vb)->vb2_queue->ops->op ? "" : " (nop)")

#define call_vb_qop(vb, op, args...)                                    \
({                                                                      \
        int err;                                                        \
                                                                        \
        log_vb_qop(vb, op);                                             \
        err = (vb)->vb2_queue->ops->op ?                                \
                (vb)->vb2_queue->ops->op(args) : 0;                     \
        if (!err)                                                       \
                (vb)->cnt_ ## op++;                                     \
        err;                                                            \
})

#define call_void_vb_qop(vb, op, args...)                               \
({                                                                      \
        log_vb_qop(vb, op);                                             \
        if ((vb)->vb2_queue->ops->op)                                   \
                (vb)->vb2_queue->ops->op(args);                         \
        (vb)->cnt_ ## op++;                                             \
})

#else

#define call_memop(vb, op, args...)                                     \
        ((vb)->vb2_queue->mem_ops->op ?                                 \
                (vb)->vb2_queue->mem_ops->op(args) : 0)

#define call_ptr_memop(vb, op, args...)                                 \
        ((vb)->vb2_queue->mem_ops->op ?                                 \
                (vb)->vb2_queue->mem_ops->op(args) : NULL)

#define call_void_memop(vb, op, args...)                                \
        do {                                                            \
                if ((vb)->vb2_queue->mem_ops->op)                       \
                        (vb)->vb2_queue->mem_ops->op(args);             \
        } while (0)

#define call_qop(q, op, args...)                                        \
        ((q)->ops->op ? (q)->ops->op(args) : 0)

#define call_void_qop(q, op, args...)                                   \
        do {                                                            \
                if ((q)->ops->op)                                       \
                        (q)->ops->op(args);                             \
        } while (0)

#define call_vb_qop(vb, op, args...)                                    \
        ((vb)->vb2_queue->ops->op ? (vb)->vb2_queue->ops->op(args) : 0)

#define call_void_vb_qop(vb, op, args...)                               \
        do {                                                            \
                if ((vb)->vb2_queue->ops->op)                           \
                        (vb)->vb2_queue->ops->op(args);                 \
        } while (0)

#endif

#define call_bufop(q, op, args...)                                      \
({                                                                      \
        int ret = 0;                                                    \
        if (q && q->buf_ops && q->buf_ops->op)                          \
                ret = q->buf_ops->op(args);                             \
        ret;                                                            \
})

#define call_void_bufop(q, op, args...)                                 \
({                                                                      \
        if (q && q->buf_ops && q->buf_ops->op)                          \
                q->buf_ops->op(args);                                   \
})

static void __vb2_queue_cancel(struct vb2_queue *q);
static void __enqueue_in_driver(struct vb2_buffer *vb);

/**
 * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
 */
static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
{
        struct vb2_queue *q = vb->vb2_queue;
        enum dma_data_direction dma_dir =
                q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
        void *mem_priv;
        int plane;
        int ret = -ENOMEM;

        /*
         * Allocate memory for all planes in this buffer
         * NOTE: mmapped areas should be page aligned
         */
        for (plane = 0; plane < vb->num_planes; ++plane) {
                unsigned long size = PAGE_ALIGN(vb->planes[plane].length);

                mem_priv = call_ptr_memop(vb, alloc,
                                q->alloc_devs[plane] ? : q->dev,
                                q->dma_attrs, size, dma_dir, q->gfp_flags);
                if (IS_ERR(mem_priv)) {
                        if (mem_priv)
                                ret = PTR_ERR(mem_priv);
                        goto free;
                }

                /* Associate allocator private data with this plane */
                vb->planes[plane].mem_priv = mem_priv;
        }

        return 0;
free:
        /* Free already allocated memory if one of the allocations failed */
        for (; plane > 0; --plane) {
                call_void_memop(vb, put, vb->planes[plane - 1].mem_priv);
                vb->planes[plane - 1].mem_priv = NULL;
        }

        return ret;
}

/**
 * __vb2_buf_mem_free() - free memory of the given buffer
 */
static void __vb2_buf_mem_free(struct vb2_buffer *vb)
{
        unsigned int plane;

        for (plane = 0; plane < vb->num_planes; ++plane) {
                call_void_memop(vb, put, vb->planes[plane].mem_priv);
                vb->planes[plane].mem_priv = NULL;
                dprintk(3, "freed plane %d of buffer %d\n", plane, vb->index);
        }
}

/**
 * __vb2_buf_userptr_put() - release userspace memory associated with
 * a USERPTR buffer
 */
static void __vb2_buf_userptr_put(struct vb2_buffer *vb)
{
        unsigned int plane;

        for (plane = 0; plane < vb->num_planes; ++plane) {
                if (vb->planes[plane].mem_priv)
                        call_void_memop(vb, put_userptr, vb->planes[plane].mem_priv);
                vb->planes[plane].mem_priv = NULL;
        }
}

/**
 * __vb2_plane_dmabuf_put() - release memory associated with
 * a DMABUF shared plane
 */
static void __vb2_plane_dmabuf_put(struct vb2_buffer *vb, struct vb2_plane *p)
{
        if (!p->mem_priv)
                return;

        if (p->dbuf_mapped)
                call_void_memop(vb, unmap_dmabuf, p->mem_priv);

        call_void_memop(vb, detach_dmabuf, p->mem_priv);
        dma_buf_put(p->dbuf);
        p->mem_priv = NULL;
        p->dbuf = NULL;
        p->dbuf_mapped = 0;
}

/**
 * __vb2_buf_dmabuf_put() - release memory associated with
 * a DMABUF shared buffer
 */
static void __vb2_buf_dmabuf_put(struct vb2_buffer *vb)
{
        unsigned int plane;

        for (plane = 0; plane < vb->num_planes; ++plane)
                __vb2_plane_dmabuf_put(vb, &vb->planes[plane]);
}

/**
 * __setup_offsets() - setup unique offsets ("cookies") for every plane in
 * the buffer.
 */
static void __setup_offsets(struct vb2_buffer *vb)
{
        struct vb2_queue *q = vb->vb2_queue;
        unsigned int plane;
        unsigned long off = 0;

        if (vb->index) {
                struct vb2_buffer *prev = q->bufs[vb->index - 1];
                struct vb2_plane *p = &prev->planes[prev->num_planes - 1];

                off = PAGE_ALIGN(p->m.offset + p->length);
        }

        for (plane = 0; plane < vb->num_planes; ++plane) {
                vb->planes[plane].m.offset = off;

                dprintk(3, "buffer %d, plane %d offset 0x%08lx\n",
                                vb->index, plane, off);

                off += vb->planes[plane].length;
                off = PAGE_ALIGN(off);
        }
}

/**
 * __vb2_queue_alloc() - allocate videobuf buffer structures and (for MMAP type)
 * video buffer memory for all buffers/planes on the queue and initializes the
 * queue
 *
 * Returns the number of buffers successfully allocated.
 */
static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
                             unsigned int num_buffers, unsigned int num_planes,
                             const unsigned plane_sizes[VB2_MAX_PLANES])
{
        unsigned int buffer, plane;
        struct vb2_buffer *vb;
        int ret;

        for (buffer = 0; buffer < num_buffers; ++buffer) {
                /* Allocate videobuf buffer structures */
                vb = kzalloc(q->buf_struct_size, GFP_KERNEL);
                if (!vb) {
                        dprintk(1, "memory alloc for buffer struct failed\n");
                        break;
                }

                vb->state = VB2_BUF_STATE_DEQUEUED;
                vb->vb2_queue = q;
                vb->num_planes = num_planes;
                vb->index = q->num_buffers + buffer;
                vb->type = q->type;
                vb->memory = memory;
                for (plane = 0; plane < num_planes; ++plane) {
                        vb->planes[plane].length = plane_sizes[plane];
                        vb->planes[plane].min_length = plane_sizes[plane];
                }
                q->bufs[vb->index] = vb;

                /* Allocate video buffer memory for the MMAP type */
                if (memory == VB2_MEMORY_MMAP) {
                        ret = __vb2_buf_mem_alloc(vb);
                        if (ret) {
                                dprintk(1, "failed allocating memory for "
                                                "buffer %d\n", buffer);
                                q->bufs[vb->index] = NULL;
                                kfree(vb);
                                break;
                        }
                        __setup_offsets(vb);
                        /*
                         * Call the driver-provided buffer initialization
                         * callback, if given. An error in initialization
                         * results in queue setup failure.
                         */
                        ret = call_vb_qop(vb, buf_init, vb);
                        if (ret) {
                                dprintk(1, "buffer %d %p initialization"
                                        " failed\n", buffer, vb);
                                __vb2_buf_mem_free(vb);
                                q->bufs[vb->index] = NULL;
                                kfree(vb);
                                break;
                        }
                }
        }

        dprintk(1, "allocated %d buffers, %d plane(s) each\n",
                        buffer, num_planes);

        return buffer;
}

/**
 * __vb2_free_mem() - release all video buffer memory for a given queue
 */
static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
{
        unsigned int buffer;
        struct vb2_buffer *vb;

        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
                vb = q->bufs[buffer];
                if (!vb)
                        continue;

                /* Free MMAP buffers or release USERPTR buffers */
                if (q->memory == VB2_MEMORY_MMAP)
                        __vb2_buf_mem_free(vb);
                else if (q->memory == VB2_MEMORY_DMABUF)
                        __vb2_buf_dmabuf_put(vb);
                else
                        __vb2_buf_userptr_put(vb);
        }
}

/**
 * __vb2_queue_free() - free buffers at the end of the queue - video memory and
 * related information, if no buffers are left return the queue to an
 * uninitialized state. Might be called even if the queue has already been freed.
 */
static int __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
{
        unsigned int buffer;

        /*
         * Sanity check: when preparing a buffer the queue lock is released for
         * a short while (see __buf_prepare for the details), which would allow
         * a race with a reqbufs which can call this function. Removing the
         * buffers from underneath __buf_prepare is obviously a bad idea, so we
         * check if any of the buffers is in the state PREPARING, and if so we
         * just return -EAGAIN.
         */
        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
                if (q->bufs[buffer] == NULL)
                        continue;
                if (q->bufs[buffer]->state == VB2_BUF_STATE_PREPARING) {
                        dprintk(1, "preparing buffers, cannot free\n");
                        return -EAGAIN;
                }
        }

        /* Call driver-provided cleanup function for each buffer, if provided */
        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
                struct vb2_buffer *vb = q->bufs[buffer];

                if (vb && vb->planes[0].mem_priv)
                        call_void_vb_qop(vb, buf_cleanup, vb);
        }

        /* Release video buffer memory */
        __vb2_free_mem(q, buffers);

#ifdef CONFIG_VIDEO_ADV_DEBUG
        /*
         * Check that all the calls were balances during the life-time of this
         * queue. If not (or if the debug level is 1 or up), then dump the
         * counters to the kernel log.
         */
        if (q->num_buffers) {
                bool unbalanced = q->cnt_start_streaming != q->cnt_stop_streaming ||
                                  q->cnt_wait_prepare != q->cnt_wait_finish;

                if (unbalanced || debug) {
                        pr_info("vb2: counters for queue %p:%s\n", q,
                                unbalanced ? " UNBALANCED!" : "");
                        pr_info("vb2:     setup: %u start_streaming: %u stop_streaming: %u\n",
                                q->cnt_queue_setup, q->cnt_start_streaming,
                                q->cnt_stop_streaming);
                        pr_info("vb2:     wait_prepare: %u wait_finish: %u\n",
                                q->cnt_wait_prepare, q->cnt_wait_finish);
                }
                q->cnt_queue_setup = 0;
                q->cnt_wait_prepare = 0;
                q->cnt_wait_finish = 0;
                q->cnt_start_streaming = 0;
                q->cnt_stop_streaming = 0;
        }
        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
                struct vb2_buffer *vb = q->bufs[buffer];
                bool unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
                                  vb->cnt_mem_prepare != vb->cnt_mem_finish ||
                                  vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
                                  vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
                                  vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
                                  vb->cnt_buf_queue != vb->cnt_buf_done ||
                                  vb->cnt_buf_prepare != vb->cnt_buf_finish ||
                                  vb->cnt_buf_init != vb->cnt_buf_cleanup;

                if (unbalanced || debug) {
                        pr_info("vb2:   counters for queue %p, buffer %d:%s\n",
                                q, buffer, unbalanced ? " UNBALANCED!" : "");
                        pr_info("vb2:     buf_init: %u buf_cleanup: %u buf_prepare: %u buf_finish: %u\n",
                                vb->cnt_buf_init, vb->cnt_buf_cleanup,
                                vb->cnt_buf_prepare, vb->cnt_buf_finish);
                        pr_info("vb2:     buf_queue: %u buf_done: %u\n",
                                vb->cnt_buf_queue, vb->cnt_buf_done);
                        pr_info("vb2:     alloc: %u put: %u prepare: %u finish: %u mmap: %u\n",
                                vb->cnt_mem_alloc, vb->cnt_mem_put,
                                vb->cnt_mem_prepare, vb->cnt_mem_finish,
                                vb->cnt_mem_mmap);
                        pr_info("vb2:     get_userptr: %u put_userptr: %u\n",
                                vb->cnt_mem_get_userptr, vb->cnt_mem_put_userptr);
                        pr_info("vb2:     attach_dmabuf: %u detach_dmabuf: %u map_dmabuf: %u unmap_dmabuf: %u\n",
                                vb->cnt_mem_attach_dmabuf, vb->cnt_mem_detach_dmabuf,
                                vb->cnt_mem_map_dmabuf, vb->cnt_mem_unmap_dmabuf);
                        pr_info("vb2:     get_dmabuf: %u num_users: %u vaddr: %u cookie: %u\n",
                                vb->cnt_mem_get_dmabuf,
                                vb->cnt_mem_num_users,
                                vb->cnt_mem_vaddr,
                                vb->cnt_mem_cookie);
                }
        }
#endif

        /* Free videobuf buffers */
        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
                kfree(q->bufs[buffer]);
                q->bufs[buffer] = NULL;
        }

        q->num_buffers -= buffers;
        if (!q->num_buffers) {
                q->memory = 0;
                INIT_LIST_HEAD(&q->queued_list);
        }
        return 0;
}

/**
 * vb2_buffer_in_use() - return true if the buffer is in use and
 * the queue cannot be freed (by the means of REQBUFS(0)) call
 */
bool vb2_buffer_in_use(struct vb2_queue *q, struct vb2_buffer *vb)
{
        unsigned int plane;
        for (plane = 0; plane < vb->num_planes; ++plane) {
                void *mem_priv = vb->planes[plane].mem_priv;
                /*
                 * If num_users() has not been provided, call_memop
                 * will return 0, apparently nobody cares about this
                 * case anyway. If num_users() returns more than 1,
                 * we are not the only user of the plane's memory.
                 */
                if (mem_priv && call_memop(vb, num_users, mem_priv) > 1)
                        return true;
        }
        return false;
}
EXPORT_SYMBOL(vb2_buffer_in_use);

/**
 * __buffers_in_use() - return true if any buffers on the queue are in use and
 * the queue cannot be freed (by the means of REQBUFS(0)) call
 */
static bool __buffers_in_use(struct vb2_queue *q)
{
        unsigned int buffer;
        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
                if (vb2_buffer_in_use(q, q->bufs[buffer]))
                        return true;
        }
        return false;
}

/**
 * vb2_core_querybuf() - query video buffer information
 * @q:          videobuf queue
 * @index:      id number of the buffer
 * @pb:         buffer struct passed from userspace
 *
 * Should be called from vidioc_querybuf ioctl handler in driver.
 * The passed buffer should have been verified.
 * This function fills the relevant information for the userspace.
 */
void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb)
{
        call_void_bufop(q, fill_user_buffer, q->bufs[index], pb);
}
EXPORT_SYMBOL_GPL(vb2_core_querybuf);

/**
 * __verify_userptr_ops() - verify that all memory operations required for
 * USERPTR queue type have been provided
 */
static int __verify_userptr_ops(struct vb2_queue *q)
{
        if (!(q->io_modes & VB2_USERPTR) || !q->mem_ops->get_userptr ||
            !q->mem_ops->put_userptr)
                return -EINVAL;

        return 0;
}

/**
 * __verify_mmap_ops() - verify that all memory operations required for
 * MMAP queue type have been provided
 */
static int __verify_mmap_ops(struct vb2_queue *q)
{
        if (!(q->io_modes & VB2_MMAP) || !q->mem_ops->alloc ||
            !q->mem_ops->put || !q->mem_ops->mmap)
                return -EINVAL;

        return 0;
}

/**
 * __verify_dmabuf_ops() - verify that all memory operations required for
 * DMABUF queue type have been provided
 */
static int __verify_dmabuf_ops(struct vb2_queue *q)
{
        if (!(q->io_modes & VB2_DMABUF) || !q->mem_ops->attach_dmabuf ||
            !q->mem_ops->detach_dmabuf  || !q->mem_ops->map_dmabuf ||
            !q->mem_ops->unmap_dmabuf)
                return -EINVAL;

        return 0;
}

/**
 * vb2_verify_memory_type() - Check whether the memory type and buffer type
 * passed to a buffer operation are compatible with the queue.
 */
int vb2_verify_memory_type(struct vb2_queue *q,
                enum vb2_memory memory, unsigned int type)
{
        if (memory != VB2_MEMORY_MMAP && memory != VB2_MEMORY_USERPTR &&
            memory != VB2_MEMORY_DMABUF) {
                dprintk(1, "unsupported memory type\n");
                return -EINVAL;
        }

        if (type != q->type) {
                dprintk(1, "requested type is incorrect\n");
                return -EINVAL;
        }

        /*
         * Make sure all the required memory ops for given memory type
         * are available.
         */
        if (memory == VB2_MEMORY_MMAP && __verify_mmap_ops(q)) {
                dprintk(1, "MMAP for current setup unsupported\n");
                return -EINVAL;
        }

        if (memory == VB2_MEMORY_USERPTR && __verify_userptr_ops(q)) {
                dprintk(1, "USERPTR for current setup unsupported\n");
                return -EINVAL;
        }

        if (memory == VB2_MEMORY_DMABUF && __verify_dmabuf_ops(q)) {
                dprintk(1, "DMABUF for current setup unsupported\n");
                return -EINVAL;
        }

        /*
         * Place the busy tests at the end: -EBUSY can be ignored when
         * create_bufs is called with count == 0, but count == 0 should still
         * do the memory and type validation.
         */
        if (vb2_fileio_is_active(q)) {
                dprintk(1, "file io in progress\n");
                return -EBUSY;
        }
        return 0;
}
EXPORT_SYMBOL(vb2_verify_memory_type);

/**
 * vb2_core_reqbufs() - Initiate streaming
 * @q:          videobuf2 queue
 * @memory: memory type
 * @count: requested buffer count
 *
 * Should be called from vidioc_reqbufs ioctl handler of a driver.
 * This function:
 * 1) verifies streaming parameters passed from the userspace,
 * 2) sets up the queue,
 * 3) negotiates number of buffers and planes per buffer with the driver
 *    to be used during streaming,
 * 4) allocates internal buffer structures (struct vb2_buffer), according to
 *    the agreed parameters,
 * 5) for MMAP memory type, allocates actual video memory, using the
 *    memory handling/allocation routines provided during queue initialization
 *
 * If req->count is 0, all the memory will be freed instead.
 * If the queue has been allocated previously (by a previous vb2_reqbufs) call
 * and the queue is not busy, memory will be reallocated.
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_reqbufs handler in driver.
 */
int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
                unsigned int *count)
{
        unsigned int num_buffers, allocated_buffers, num_planes = 0;
        unsigned plane_sizes[VB2_MAX_PLANES] = { };
        int ret;

        if (q->streaming) {
                dprintk(1, "streaming active\n");
                return -EBUSY;
        }

        if (*count == 0 || q->num_buffers != 0 || q->memory != memory) {
                /*
                 * We already have buffers allocated, so first check if they
                 * are not in use and can be freed.
                 */
                mutex_lock(&q->mmap_lock);
                if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) {
                        mutex_unlock(&q->mmap_lock);
                        dprintk(1, "memory in use, cannot free\n");
                        return -EBUSY;
                }

                /*
                 * Call queue_cancel to clean up any buffers in the PREPARED or
                 * QUEUED state which is possible if buffers were prepared or
                 * queued without ever calling STREAMON.
                 */
                __vb2_queue_cancel(q);
                ret = __vb2_queue_free(q, q->num_buffers);
                mutex_unlock(&q->mmap_lock);
                if (ret)
                        return ret;

                /*
                 * In case of REQBUFS(0) return immediately without calling
                 * driver's queue_setup() callback and allocating resources.
                 */
                if (*count == 0)
                        return 0;
        }

        /*
         * Make sure the requested values and current defaults are sane.
         */
        num_buffers = min_t(unsigned int, *count, VB2_MAX_FRAME);
        num_buffers = max_t(unsigned int, num_buffers, q->min_buffers_needed);
        memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
        q->memory = memory;

        /*
         * Ask the driver how many buffers and planes per buffer it requires.
         * Driver also sets the size and allocator context for each plane.
         */
        ret = call_qop(q, queue_setup, q, &num_buffers, &num_planes,
                       plane_sizes, q->alloc_devs);
        if (ret)
                return ret;

        /* Finally, allocate buffers and video memory */
        allocated_buffers =
                __vb2_queue_alloc(q, memory, num_buffers, num_planes, plane_sizes);
        if (allocated_buffers == 0) {
                dprintk(1, "memory allocation failed\n");
                return -ENOMEM;
        }

        /*
         * There is no point in continuing if we can't allocate the minimum
         * number of buffers needed by this vb2_queue.
         */
        if (allocated_buffers < q->min_buffers_needed)
                ret = -ENOMEM;

        /*
         * Check if driver can handle the allocated number of buffers.
         */
        if (!ret && allocated_buffers < num_buffers) {
                num_buffers = allocated_buffers;
                /*
                 * num_planes is set by the previous queue_setup(), but since it
                 * signals to queue_setup() whether it is called from create_bufs()
                 * vs reqbufs() we zero it here to signal that queue_setup() is
                 * called for the reqbufs() case.
                 */
                num_planes = 0;

                ret = call_qop(q, queue_setup, q, &num_buffers,
                               &num_planes, plane_sizes, q->alloc_devs);

                if (!ret && allocated_buffers < num_buffers)
                        ret = -ENOMEM;

                /*
                 * Either the driver has accepted a smaller number of buffers,
                 * or .queue_setup() returned an error
                 */
        }

        mutex_lock(&q->mmap_lock);
        q->num_buffers = allocated_buffers;

        if (ret < 0) {
                /*
                 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
                 * from q->num_buffers.
                 */
                __vb2_queue_free(q, allocated_buffers);
                mutex_unlock(&q->mmap_lock);
                return ret;
        }
        mutex_unlock(&q->mmap_lock);

        /*
         * Return the number of successfully allocated buffers
         * to the userspace.
         */
        *count = allocated_buffers;
        q->waiting_for_buffers = !q->is_output;

        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_reqbufs);

/**
 * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
 * @q:          videobuf2 queue
 * @memory: memory type
 * @count: requested buffer count
 * @parg: parameter passed to device driver
 *
 * Should be called from vidioc_create_bufs ioctl handler of a driver.
 * This function:
 * 1) verifies parameter sanity
 * 2) calls the .queue_setup() queue operation
 * 3) performs any necessary memory allocations
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_create_bufs handler in driver.
 */
int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
                unsigned int *count, unsigned requested_planes,
                const unsigned requested_sizes[])
{
        unsigned int num_planes = 0, num_buffers, allocated_buffers;
        unsigned plane_sizes[VB2_MAX_PLANES] = { };
        int ret;

        if (q->num_buffers == VB2_MAX_FRAME) {
                dprintk(1, "maximum number of buffers already allocated\n");
                return -ENOBUFS;
        }

        if (!q->num_buffers) {
                memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
                q->memory = memory;
                q->waiting_for_buffers = !q->is_output;
        }

        num_buffers = min(*count, VB2_MAX_FRAME - q->num_buffers);

        if (requested_planes && requested_sizes) {
                num_planes = requested_planes;
                memcpy(plane_sizes, requested_sizes, sizeof(plane_sizes));
        }

        /*
         * Ask the driver, whether the requested number of buffers, planes per
         * buffer and their sizes are acceptable
         */
        ret = call_qop(q, queue_setup, q, &num_buffers,
                       &num_planes, plane_sizes, q->alloc_devs);
        if (ret)
                return ret;

        /* Finally, allocate buffers and video memory */
        allocated_buffers = __vb2_queue_alloc(q, memory, num_buffers,
                                num_planes, plane_sizes);
        if (allocated_buffers == 0) {
                dprintk(1, "memory allocation failed\n");
                return -ENOMEM;
        }

        /*
         * Check if driver can handle the so far allocated number of buffers.
         */
        if (allocated_buffers < num_buffers) {
                num_buffers = allocated_buffers;

                /*
                 * q->num_buffers contains the total number of buffers, that the
                 * queue driver has set up
                 */
                ret = call_qop(q, queue_setup, q, &num_buffers,
                               &num_planes, plane_sizes, q->alloc_devs);

                if (!ret && allocated_buffers < num_buffers)
                        ret = -ENOMEM;

                /*
                 * Either the driver has accepted a smaller number of buffers,
                 * or .queue_setup() returned an error
                 */
        }

        mutex_lock(&q->mmap_lock);
        q->num_buffers += allocated_buffers;

        if (ret < 0) {
                /*
                 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
                 * from q->num_buffers.
                 */
                __vb2_queue_free(q, allocated_buffers);
                mutex_unlock(&q->mmap_lock);
                return -ENOMEM;
        }
        mutex_unlock(&q->mmap_lock);

        /*
         * Return the number of successfully allocated buffers
         * to the userspace.
         */
        *count = allocated_buffers;

        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_create_bufs);

/**
 * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
 * @vb:         vb2_buffer to which the plane in question belongs to
 * @plane_no:   plane number for which the address is to be returned
 *
 * This function returns a kernel virtual address of a given plane if
 * such a mapping exist, NULL otherwise.
 */
void *vb2_plane_vaddr(struct vb2_buffer *vb, unsigned int plane_no)
{
        if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
                return NULL;

        return call_ptr_memop(vb, vaddr, vb->planes[plane_no].mem_priv);

}
EXPORT_SYMBOL_GPL(vb2_plane_vaddr);

/**
 * vb2_plane_cookie() - Return allocator specific cookie for the given plane
 * @vb:         vb2_buffer to which the plane in question belongs to
 * @plane_no:   plane number for which the cookie is to be returned
 *
 * This function returns an allocator specific cookie for a given plane if
 * available, NULL otherwise. The allocator should provide some simple static
 * inline function, which would convert this cookie to the allocator specific
 * type that can be used directly by the driver to access the buffer. This can
 * be for example physical address, pointer to scatter list or IOMMU mapping.
 */
void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
{
        if (plane_no >= vb->num_planes || !vb->planes[plane_no].mem_priv)
                return NULL;

        return call_ptr_memop(vb, cookie, vb->planes[plane_no].mem_priv);
}
EXPORT_SYMBOL_GPL(vb2_plane_cookie);

/**
 * vb2_buffer_done() - inform videobuf that an operation on a buffer is finished
 * @vb:         vb2_buffer returned from the driver
 * @state:      either VB2_BUF_STATE_DONE if the operation finished successfully,
 *              VB2_BUF_STATE_ERROR if the operation finished with an error or
 *              VB2_BUF_STATE_QUEUED if the driver wants to requeue buffers.
 *              If start_streaming fails then it should return buffers with state
 *              VB2_BUF_STATE_QUEUED to put them back into the queue.
 *
 * This function should be called by the driver after a hardware operation on
 * a buffer is finished and the buffer may be returned to userspace. The driver
 * cannot use this buffer anymore until it is queued back to it by videobuf
 * by the means of buf_queue callback. Only buffers previously queued to the
 * driver by buf_queue can be passed to this function.
 *
 * While streaming a buffer can only be returned in state DONE or ERROR.
 * The start_streaming op can also return them in case the DMA engine cannot
 * be started for some reason. In that case the buffers should be returned with
 * state QUEUED.
 */
void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
{
        struct vb2_queue *q = vb->vb2_queue;
        unsigned long flags;
        unsigned int plane;

        if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
                return;

        if (WARN_ON(state != VB2_BUF_STATE_DONE &&
                    state != VB2_BUF_STATE_ERROR &&
                    state != VB2_BUF_STATE_QUEUED &&
                    state != VB2_BUF_STATE_REQUEUEING))
                state = VB2_BUF_STATE_ERROR;

#ifdef CONFIG_VIDEO_ADV_DEBUG
        /*
         * Although this is not a callback, it still does have to balance
         * with the buf_queue op. So update this counter manually.
         */
        vb->cnt_buf_done++;
#endif
        dprintk(4, "done processing on buffer %d, state: %d\n",
                        vb->index, state);

        /* sync buffers */
        for (plane = 0; plane < vb->num_planes; ++plane)
                call_void_memop(vb, finish, vb->planes[plane].mem_priv);

        spin_lock_irqsave(&q->done_lock, flags);
        if (state == VB2_BUF_STATE_QUEUED ||
            state == VB2_BUF_STATE_REQUEUEING) {
                vb->state = VB2_BUF_STATE_QUEUED;
        } else {
                /* Add the buffer to the done buffers list */
                list_add_tail(&vb->done_entry, &q->done_list);
                vb->state = state;
        }
        atomic_dec(&q->owned_by_drv_count);
        spin_unlock_irqrestore(&q->done_lock, flags);

        trace_vb2_buf_done(q, vb);

        switch (state) {
        case VB2_BUF_STATE_QUEUED:
                return;
        case VB2_BUF_STATE_REQUEUEING:
                if (q->start_streaming_called)
                        __enqueue_in_driver(vb);
                return;
        default:
                /* Inform any processes that may be waiting for buffers */
                wake_up(&q->done_wq);
                break;
        }
}
EXPORT_SYMBOL_GPL(vb2_buffer_done);

/**
 * vb2_discard_done() - discard all buffers marked as DONE
 * @q:          videobuf2 queue
 *
 * This function is intended to be used with suspend/resume operations. It
 * discards all 'done' buffers as they would be too old to be requested after
 * resume.
 *
 * Drivers must stop the hardware and synchronize with interrupt handlers and/or
 * delayed works before calling this function to make sure no buffer will be
 * touched by the driver and/or hardware.
 */
void vb2_discard_done(struct vb2_queue *q)
{
        struct vb2_buffer *vb;
        unsigned long flags;

        spin_lock_irqsave(&q->done_lock, flags);
        list_for_each_entry(vb, &q->done_list, done_entry)
                vb->state = VB2_BUF_STATE_ERROR;
        spin_unlock_irqrestore(&q->done_lock, flags);
}
EXPORT_SYMBOL_GPL(vb2_discard_done);

/**
 * __qbuf_mmap() - handle qbuf of an MMAP buffer
 */
static int __qbuf_mmap(struct vb2_buffer *vb, const void *pb)
{
        int ret = 0;

        if (pb)
                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
                                 vb, pb, vb->planes);
        return ret ? ret : call_vb_qop(vb, buf_prepare, vb);
}

/**
 * __qbuf_userptr() - handle qbuf of a USERPTR buffer
 */
static int __qbuf_userptr(struct vb2_buffer *vb, const void *pb)
{
        struct vb2_plane planes[VB2_MAX_PLANES];
        struct vb2_queue *q = vb->vb2_queue;
        void *mem_priv;
        unsigned int plane;
        int ret = 0;
        enum dma_data_direction dma_dir =
                q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
        bool reacquired = vb->planes[0].mem_priv == NULL;

        memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
        /* Copy relevant information provided by the userspace */
        if (pb)
                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
                                 vb, pb, planes);
        if (ret)
                return ret;

        for (plane = 0; plane < vb->num_planes; ++plane) {
                /* Skip the plane if already verified */
                if (vb->planes[plane].m.userptr &&
                        vb->planes[plane].m.userptr == planes[plane].m.userptr
                        && vb->planes[plane].length == planes[plane].length)
                        continue;

                dprintk(3, "userspace address for plane %d changed, "
                                "reacquiring memory\n", plane);

                /* Check if the provided plane buffer is large enough */
                if (planes[plane].length < vb->planes[plane].min_length) {
                        dprintk(1, "provided buffer size %u is less than "
                                                "setup size %u for plane %d\n",
                                                planes[plane].length,
                                                vb->planes[plane].min_length,
                                                plane);
                        ret = -EINVAL;
                        goto err;
                }

                /* Release previously acquired memory if present */
                if (vb->planes[plane].mem_priv) {
                        if (!reacquired) {
                                reacquired = true;
                                call_void_vb_qop(vb, buf_cleanup, vb);
                        }
                        call_void_memop(vb, put_userptr, vb->planes[plane].mem_priv);
                }

                vb->planes[plane].mem_priv = NULL;
                vb->planes[plane].bytesused = 0;
                vb->planes[plane].length = 0;
                vb->planes[plane].m.userptr = 0;
                vb->planes[plane].data_offset = 0;

                /* Acquire each plane's memory */
                mem_priv = call_ptr_memop(vb, get_userptr,
                                q->alloc_devs[plane] ? : q->dev,
                                planes[plane].m.userptr,
                                planes[plane].length, dma_dir);
                if (IS_ERR(mem_priv)) {
                        dprintk(1, "failed acquiring userspace "
                                                "memory for plane %d\n", plane);
                        ret = PTR_ERR(mem_priv);
                        goto err;
                }
                vb->planes[plane].mem_priv = mem_priv;
        }

        /*
         * Now that everything is in order, copy relevant information
         * provided by userspace.
         */
        for (plane = 0; plane < vb->num_planes; ++plane) {
                vb->planes[plane].bytesused = planes[plane].bytesused;
                vb->planes[plane].length = planes[plane].length;
                vb->planes[plane].m.userptr = planes[plane].m.userptr;
                vb->planes[plane].data_offset = planes[plane].data_offset;
        }

        if (reacquired) {
                /*
                 * One or more planes changed, so we must call buf_init to do
                 * the driver-specific initialization on the newly acquired
                 * buffer, if provided.
                 */
                ret = call_vb_qop(vb, buf_init, vb);
                if (ret) {
                        dprintk(1, "buffer initialization failed\n");
                        goto err;
                }
        }

        ret = call_vb_qop(vb, buf_prepare, vb);
        if (ret) {
                dprintk(1, "buffer preparation failed\n");
                call_void_vb_qop(vb, buf_cleanup, vb);
                goto err;
        }

        return 0;
err:
        /* In case of errors, release planes that were already acquired */
        for (plane = 0; plane < vb->num_planes; ++plane) {
                if (vb->planes[plane].mem_priv)
                        call_void_memop(vb, put_userptr,
                                vb->planes[plane].mem_priv);
                vb->planes[plane].mem_priv = NULL;
                vb->planes[plane].m.userptr = 0;
                vb->planes[plane].length = 0;
        }

        return ret;
}

/**
 * __qbuf_dmabuf() - handle qbuf of a DMABUF buffer
 */
static int __qbuf_dmabuf(struct vb2_buffer *vb, const void *pb)
{
        struct vb2_plane planes[VB2_MAX_PLANES];
        struct vb2_queue *q = vb->vb2_queue;
        void *mem_priv;
        unsigned int plane;
        int ret = 0;
        enum dma_data_direction dma_dir =
                q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
        bool reacquired = vb->planes[0].mem_priv == NULL;

        memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
        /* Copy relevant information provided by the userspace */
        if (pb)
                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
                                 vb, pb, planes);
        if (ret)
                return ret;

        for (plane = 0; plane < vb->num_planes; ++plane) {
                struct dma_buf *dbuf = dma_buf_get(planes[plane].m.fd);

                if (IS_ERR_OR_NULL(dbuf)) {
                        dprintk(1, "invalid dmabuf fd for plane %d\n",
                                plane);
                        ret = -EINVAL;
                        goto err;
                }

                /* use DMABUF size if length is not provided */
                if (planes[plane].length == 0)
                        planes[plane].length = dbuf->size;

                if (planes[plane].length < vb->planes[plane].min_length) {
                        dprintk(1, "invalid dmabuf length %u for plane %d, "
                                "minimum length %u\n",
                                planes[plane].length, plane,
                                vb->planes[plane].min_length);
                        dma_buf_put(dbuf);
                        ret = -EINVAL;
                        goto err;
                }

                /* Skip the plane if already verified */
                if (dbuf == vb->planes[plane].dbuf &&
                        vb->planes[plane].length == planes[plane].length) {
                        dma_buf_put(dbuf);
                        continue;
                }

                dprintk(1, "buffer for plane %d changed\n", plane);

                if (!reacquired) {
                        reacquired = true;
                        call_void_vb_qop(vb, buf_cleanup, vb);
                }

                /* Release previously acquired memory if present */
                __vb2_plane_dmabuf_put(vb, &vb->planes[plane]);
                vb->planes[plane].bytesused = 0;
                vb->planes[plane].length = 0;
                vb->planes[plane].m.fd = 0;
                vb->planes[plane].data_offset = 0;

                /* Acquire each plane's memory */
                mem_priv = call_ptr_memop(vb, attach_dmabuf,
                                q->alloc_devs[plane] ? : q->dev,
                                dbuf, planes[plane].length, dma_dir);
                if (IS_ERR(mem_priv)) {
                        dprintk(1, "failed to attach dmabuf\n");
                        ret = PTR_ERR(mem_priv);
                        dma_buf_put(dbuf);
                        goto err;
                }

                vb->planes[plane].dbuf = dbuf;
                vb->planes[plane].mem_priv = mem_priv;
        }

        /*
         * This pins the buffer(s) with dma_buf_map_attachment()). It's done
         * here instead just before the DMA, while queueing the buffer(s) so
         * userspace knows sooner rather than later if the dma-buf map fails.
         */
        for (plane = 0; plane < vb->num_planes; ++plane) {
                ret = call_memop(vb, map_dmabuf, vb->planes[plane].mem_priv);
                if (ret) {
                        dprintk(1, "failed to map dmabuf for plane %d\n",
                                plane);
                        goto err;
                }
                vb->planes[plane].dbuf_mapped = 1;
        }

        /*
         * Now that everything is in order, copy relevant information
         * provided by userspace.
         */
        for (plane = 0; plane < vb->num_planes; ++plane) {
                vb->planes[plane].bytesused = planes[plane].bytesused;
                vb->planes[plane].length = planes[plane].length;
                vb->planes[plane].m.fd = planes[plane].m.fd;
                vb->planes[plane].data_offset = planes[plane].data_offset;
        }

        if (reacquired) {
                /*
                 * Call driver-specific initialization on the newly acquired buffer,
                 * if provided.
                 */
                ret = call_vb_qop(vb, buf_init, vb);
                if (ret) {
                        dprintk(1, "buffer initialization failed\n");
                        goto err;
                }
        }

        ret = call_vb_qop(vb, buf_prepare, vb);
        if (ret) {
                dprintk(1, "buffer preparation failed\n");
                call_void_vb_qop(vb, buf_cleanup, vb);
                goto err;
        }

        return 0;
err:
        /* In case of errors, release planes that were already acquired */
        __vb2_buf_dmabuf_put(vb);

        return ret;
}

/**
 * __enqueue_in_driver() - enqueue a vb2_buffer in driver for processing
 */
static void __enqueue_in_driver(struct vb2_buffer *vb)
{
        struct vb2_queue *q = vb->vb2_queue;
        unsigned int plane;

        vb->state = VB2_BUF_STATE_ACTIVE;
        atomic_inc(&q->owned_by_drv_count);

        trace_vb2_buf_queue(q, vb);

        /* sync buffers */
        for (plane = 0; plane < vb->num_planes; ++plane)
                call_void_memop(vb, prepare, vb->planes[plane].mem_priv);

        call_void_vb_qop(vb, buf_queue, vb);
}

static int __buf_prepare(struct vb2_buffer *vb, const void *pb)
{
        struct vb2_queue *q = vb->vb2_queue;
        int ret;

        if (q->error) {
                dprintk(1, "fatal error occurred on queue\n");
                return -EIO;
        }

        vb->state = VB2_BUF_STATE_PREPARING;

        switch (q->memory) {
        case VB2_MEMORY_MMAP:
                ret = __qbuf_mmap(vb, pb);
                break;
        case VB2_MEMORY_USERPTR:
                ret = __qbuf_userptr(vb, pb);
                break;
        case VB2_MEMORY_DMABUF:
                ret = __qbuf_dmabuf(vb, pb);
                break;
        default:
                WARN(1, "Invalid queue type\n");
                ret = -EINVAL;
        }

        if (ret)
                dprintk(1, "buffer preparation failed: %d\n", ret);
        vb->state = ret ? VB2_BUF_STATE_DEQUEUED : VB2_BUF_STATE_PREPARED;

        return ret;
}

/**
 * vb2_core_prepare_buf() - Pass ownership of a buffer from userspace
 *                      to the kernel
 * @q:          videobuf2 queue
 * @index:      id number of the buffer
 * @pb:         buffer structure passed from userspace to vidioc_prepare_buf
 *              handler in driver
 *
 * Should be called from vidioc_prepare_buf ioctl handler of a driver.
 * The passed buffer should have been verified.
 * This function calls buf_prepare callback in the driver (if provided),
 * in which driver-specific buffer initialization can be performed,
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_prepare_buf handler in driver.
 */
int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
{
        struct vb2_buffer *vb;
        int ret;

        vb = q->bufs[index];
        if (vb->state != VB2_BUF_STATE_DEQUEUED) {
                dprintk(1, "invalid buffer state %d\n",
                        vb->state);
                return -EINVAL;
        }

        ret = __buf_prepare(vb, pb);
        if (ret)
                return ret;

        /* Fill buffer information for the userspace */
        call_void_bufop(q, fill_user_buffer, vb, pb);

        dprintk(1, "prepare of buffer %d succeeded\n", vb->index);

        return ret;
}
EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);

/**
 * vb2_start_streaming() - Attempt to start streaming.
 * @q:          videobuf2 queue
 *
 * Attempt to start streaming. When this function is called there must be
 * at least q->min_buffers_needed buffers queued up (i.e. the minimum
 * number of buffers required for the DMA engine to function). If the
 * @start_streaming op fails it is supposed to return all the driver-owned
 * buffers back to vb2 in state QUEUED. Check if that happened and if
 * not warn and reclaim them forcefully.
 */
static int vb2_start_streaming(struct vb2_queue *q)
{
        struct vb2_buffer *vb;
        int ret;

        /*
         * If any buffers were queued before streamon,
         * we can now pass them to driver for processing.
         */
        list_for_each_entry(vb, &q->queued_list, queued_entry)
                __enqueue_in_driver(vb);

        /* Tell the driver to start streaming */
        q->start_streaming_called = 1;
        ret = call_qop(q, start_streaming, q,
                       atomic_read(&q->owned_by_drv_count));
        if (!ret)
                return 0;

        q->start_streaming_called = 0;

        dprintk(1, "driver refused to start streaming\n");
        /*
         * If you see this warning, then the driver isn't cleaning up properly
         * after a failed start_streaming(). See the start_streaming()
         * documentation in videobuf2-core.h for more information how buffers
         * should be returned to vb2 in start_streaming().
         */
        if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
                unsigned i;

                /*
                 * Forcefully reclaim buffers if the driver did not
                 * correctly return them to vb2.
                 */
                for (i = 0; i < q->num_buffers; ++i) {
                        vb = q->bufs[i];
                        if (vb->state == VB2_BUF_STATE_ACTIVE)
                                vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED);
                }
                /* Must be zero now */
                WARN_ON(atomic_read(&q->owned_by_drv_count));
        }
        /*
         * If done_list is not empty, then start_streaming() didn't call
         * vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED) but STATE_ERROR or
         * STATE_DONE.
         */
        WARN_ON(!list_empty(&q->done_list));
        return ret;
}

/**
 * vb2_core_qbuf() - Queue a buffer from userspace
 * @q:          videobuf2 queue
 * @index:      id number of the buffer
 * @pb:         buffer structure passed from userspace to vidioc_qbuf handler
 *              in driver
 *
 * Should be called from vidioc_qbuf ioctl handler of a driver.
 * The passed buffer should have been verified.
 * This function:
 * 1) if necessary, calls buf_prepare callback in the driver (if provided), in
 *    which driver-specific buffer initialization can be performed,
 * 2) if streaming is on, queues the buffer in driver by the means of buf_queue
 *    callback for processing.
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_qbuf handler in driver.
 */
int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
{
        struct vb2_buffer *vb;
        int ret;

        vb = q->bufs[index];

        switch (vb->state) {
        case VB2_BUF_STATE_DEQUEUED:
                ret = __buf_prepare(vb, pb);
                if (ret)
                        return ret;
                break;
        case VB2_BUF_STATE_PREPARED:
                break;
        case VB2_BUF_STATE_PREPARING:
                dprintk(1, "buffer still being prepared\n");
                return -EINVAL;
        default:
                dprintk(1, "invalid buffer state %d\n", vb->state);
                return -EINVAL;
        }

        /*
         * Add to the queued buffers list, a buffer will stay on it until
         * dequeued in dqbuf.
         */
        list_add_tail(&vb->queued_entry, &q->queued_list);
        q->queued_count++;
        q->waiting_for_buffers = false;
        vb->state = VB2_BUF_STATE_QUEUED;

        if (pb)
                call_void_bufop(q, copy_timestamp, vb, pb);

        trace_vb2_qbuf(q, vb);

        /*
         * If already streaming, give the buffer to driver for processing.
         * If not, the buffer will be given to driver on next streamon.
         */
        if (q->start_streaming_called)
                __enqueue_in_driver(vb);

        /* Fill buffer information for the userspace */
        if (pb)
                call_void_bufop(q, fill_user_buffer, vb, pb);

        /*
         * If streamon has been called, and we haven't yet called
         * start_streaming() since not enough buffers were queued, and
         * we now have reached the minimum number of queued buffers,
         * then we can finally call start_streaming().
         */
        if (q->streaming && !q->start_streaming_called &&
            q->queued_count >= q->min_buffers_needed) {
                ret = vb2_start_streaming(q);
                if (ret)
                        return ret;
        }

        dprintk(1, "qbuf of buffer %d succeeded\n", vb->index);
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_qbuf);

/**
 * __vb2_wait_for_done_vb() - wait for a buffer to become available
 * for dequeuing
 *
 * Will sleep if required for nonblocking == false.
 */
static int __vb2_wait_for_done_vb(struct vb2_queue *q, int nonblocking)
{
        /*
         * All operations on vb_done_list are performed under done_lock
         * spinlock protection. However, buffers may be removed from
         * it and returned to userspace only while holding both driver's
         * lock and the done_lock spinlock. Thus we can be sure that as
         * long as we hold the driver's lock, the list will remain not
         * empty if list_empty() check succeeds.
         */

        for (;;) {
                int ret;

                if (!q->streaming) {
                        dprintk(1, "streaming off, will not wait for buffers\n");
                        return -EINVAL;
                }

                if (q->error) {
                        dprintk(1, "Queue in error state, will not wait for buffers\n");
                        return -EIO;
                }

                if (q->last_buffer_dequeued) {
                        dprintk(3, "last buffer dequeued already, will not wait for buffers\n");
                        return -EPIPE;
                }

                if (!list_empty(&q->done_list)) {
                        /*
                         * Found a buffer that we were waiting for.
                         */
                        break;
                }

                if (nonblocking) {
                        dprintk(1, "nonblocking and no buffers to dequeue, "
                                                                "will not wait\n");
                        return -EAGAIN;
                }

                /*
                 * We are streaming and blocking, wait for another buffer to
                 * become ready or for streamoff. Driver's lock is released to
                 * allow streamoff or qbuf to be called while waiting.
                 */
                call_void_qop(q, wait_prepare, q);

                /*
                 * All locks have been released, it is safe to sleep now.
                 */
                dprintk(3, "will sleep waiting for buffers\n");
                ret = wait_event_interruptible(q->done_wq,
                                !list_empty(&q->done_list) || !q->streaming ||
                                q->error);

                /*
                 * We need to reevaluate both conditions again after reacquiring
                 * the locks or return an error if one occurred.
                 */
                call_void_qop(q, wait_finish, q);
                if (ret) {
                        dprintk(1, "sleep was interrupted\n");
                        return ret;
                }
        }
        return 0;
}

/**
 * __vb2_get_done_vb() - get a buffer ready for dequeuing
 *
 * Will sleep if required for nonblocking == false.
 */
static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
                             void *pb, int nonblocking)
{
        unsigned long flags;
        int ret = 0;

        /*
         * Wait for at least one buffer to become available on the done_list.
         */
        ret = __vb2_wait_for_done_vb(q, nonblocking);
        if (ret)
                return ret;

        /*
         * Driver's lock has been held since we last verified that done_list
         * is not empty, so no need for another list_empty(done_list) check.
         */
        spin_lock_irqsave(&q->done_lock, flags);
        *vb = list_first_entry(&q->done_list, struct vb2_buffer, done_entry);
        /*
         * Only remove the buffer from done_list if all planes can be
         * handled. Some cases such as V4L2 file I/O and DVB have pb
         * == NULL; skip the check then as there's nothing to verify.
         */
        if (pb)
                ret = call_bufop(q, verify_planes_array, *vb, pb);
        if (!ret)
                list_del(&(*vb)->done_entry);
        spin_unlock_irqrestore(&q->done_lock, flags);

        return ret;
}

/**
 * vb2_wait_for_all_buffers() - wait until all buffers are given back to vb2
 * @q:          videobuf2 queue
 *
 * This function will wait until all buffers that have been given to the driver
 * by buf_queue() are given back to vb2 with vb2_buffer_done(). It doesn't call
 * wait_prepare, wait_finish pair. It is intended to be called with all locks
 * taken, for example from stop_streaming() callback.
 */
int vb2_wait_for_all_buffers(struct vb2_queue *q)
{
        if (!q->streaming) {
                dprintk(1, "streaming off, will not wait for buffers\n");
                return -EINVAL;
        }

        if (q->start_streaming_called)
                wait_event(q->done_wq, !atomic_read(&q->owned_by_drv_count));
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_wait_for_all_buffers);

/**
 * __vb2_dqbuf() - bring back the buffer to the DEQUEUED state
 */
static void __vb2_dqbuf(struct vb2_buffer *vb)
{
        struct vb2_queue *q = vb->vb2_queue;
        unsigned int i;

        /* nothing to do if the buffer is already dequeued */
        if (vb->state == VB2_BUF_STATE_DEQUEUED)
                return;

        vb->state = VB2_BUF_STATE_DEQUEUED;

        /* unmap DMABUF buffer */
        if (q->memory == VB2_MEMORY_DMABUF)
                for (i = 0; i < vb->num_planes; ++i) {
                        if (!vb->planes[i].dbuf_mapped)
                                continue;
                        call_void_memop(vb, unmap_dmabuf, vb->planes[i].mem_priv);
                        vb->planes[i].dbuf_mapped = 0;
                }
}

/**
 * vb2_dqbuf() - Dequeue a buffer to the userspace
 * @q:          videobuf2 queue
 * @pb:         buffer structure passed from userspace to vidioc_dqbuf handler
 *              in driver
 * @nonblocking: if true, this call will not sleep waiting for a buffer if no
 *               buffers ready for dequeuing are present. Normally the driver
 *               would be passing (file->f_flags & O_NONBLOCK) here
 *
 * Should be called from vidioc_dqbuf ioctl handler of a driver.
 * The passed buffer should have been verified.
 * This function:
 * 1) calls buf_finish callback in the driver (if provided), in which
 *    driver can perform any additional operations that may be required before
 *    returning the buffer to userspace, such as cache sync,
 * 2) the buffer struct members are filled with relevant information for
 *    the userspace.
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_dqbuf handler in driver.
 */
int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
                   bool nonblocking)
{
        struct vb2_buffer *vb = NULL;
        int ret;

        ret = __vb2_get_done_vb(q, &vb, pb, nonblocking);
        if (ret < 0)
                return ret;

        switch (vb->state) {
        case VB2_BUF_STATE_DONE:
                dprintk(3, "returning done buffer\n");
                break;
        case VB2_BUF_STATE_ERROR:
                dprintk(3, "returning done buffer with errors\n");
                break;
        default:
                dprintk(1, "invalid buffer state\n");
                return -EINVAL;
        }

        call_void_vb_qop(vb, buf_finish, vb);

        if (pindex)
                *pindex = vb->index;

        /* Fill buffer information for the userspace */
        if (pb)
                call_void_bufop(q, fill_user_buffer, vb, pb);

        /* Remove from videobuf queue */
        list_del(&vb->queued_entry);
        q->queued_count--;

        trace_vb2_dqbuf(q, vb);

        /* go back to dequeued state */
        __vb2_dqbuf(vb);

        dprintk(1, "dqbuf of buffer %d, with state %d\n",
                        vb->index, vb->state);

        return 0;

}
EXPORT_SYMBOL_GPL(vb2_core_dqbuf);

/**
 * __vb2_queue_cancel() - cancel and stop (pause) streaming
 *
 * Removes all queued buffers from driver's queue and all buffers queued by
 * userspace from videobuf's queue. Returns to state after reqbufs.
 */
static void __vb2_queue_cancel(struct vb2_queue *q)
{
        unsigned int i;

        /*
         * Tell driver to stop all transactions and release all queued
         * buffers.
         */
        if (q->start_streaming_called)
                call_void_qop(q, stop_streaming, q);

        /*
         * If you see this warning, then the driver isn't cleaning up properly
         * in stop_streaming(). See the stop_streaming() documentation in
         * videobuf2-core.h for more information how buffers should be returned
         * to vb2 in stop_streaming().
         */
        if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
                for (i = 0; i < q->num_buffers; ++i)
                        if (q->bufs[i]->state == VB2_BUF_STATE_ACTIVE)
                                vb2_buffer_done(q->bufs[i], VB2_BUF_STATE_ERROR);
                /* Must be zero now */
                WARN_ON(atomic_read(&q->owned_by_drv_count));
        }

        q->streaming = 0;
        q->start_streaming_called = 0;
        q->queued_count = 0;
        q->error = 0;

        /*
         * Remove all buffers from videobuf's list...
         */
        INIT_LIST_HEAD(&q->queued_list);
        /*
         * ...and done list; userspace will not receive any buffers it
         * has not already dequeued before initiating cancel.
         */
        INIT_LIST_HEAD(&q->done_list);
        atomic_set(&q->owned_by_drv_count, 0);
        wake_up_all(&q->done_wq);

        /*
         * Reinitialize all buffers for next use.
         * Make sure to call buf_finish for any queued buffers. Normally
         * that's done in dqbuf, but that's not going to happen when we
         * cancel the whole queue. Note: this code belongs here, not in
         * __vb2_dqbuf() since in vb2_core_dqbuf() there is a critical
         * call to __fill_user_buffer() after buf_finish(). That order can't
         * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
         */
        for (i = 0; i < q->num_buffers; ++i) {
                struct vb2_buffer *vb = q->bufs[i];

                if (vb->state != VB2_BUF_STATE_DEQUEUED) {
                        vb->state = VB2_BUF_STATE_PREPARED;
                        call_void_vb_qop(vb, buf_finish, vb);
                }
                __vb2_dqbuf(vb);
        }
}

int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
{
        int ret;

        if (type != q->type) {
                dprintk(1, "invalid stream type\n");
                return -EINVAL;
        }

        if (q->streaming) {
                dprintk(3, "already streaming\n");
                return 0;
        }

        if (!q->num_buffers) {
                dprintk(1, "no buffers have been allocated\n");
                return -EINVAL;
        }

        if (q->num_buffers < q->min_buffers_needed) {
                dprintk(1, "need at least %u allocated buffers\n",
                                q->min_buffers_needed);
                return -EINVAL;
        }

        /*
         * Tell driver to start streaming provided sufficient buffers
         * are available.
         */
        if (q->queued_count >= q->min_buffers_needed) {
                ret = v4l_vb2q_enable_media_source(q);
                if (ret)
                        return ret;
                ret = vb2_start_streaming(q);
                if (ret) {
                        __vb2_queue_cancel(q);
                        return ret;
                }
        }

        q->streaming = 1;

        dprintk(3, "successful\n");
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_streamon);

/**
 * vb2_queue_error() - signal a fatal error on the queue
 * @q:          videobuf2 queue
 *
 * Flag that a fatal unrecoverable error has occurred and wake up all processes
 * waiting on the queue. Polling will now set POLLERR and queuing and dequeuing
 * buffers will return -EIO.
 *
 * The error flag will be cleared when cancelling the queue, either from
 * vb2_streamoff or vb2_queue_release. Drivers should thus not call this
 * function before starting the stream, otherwise the error flag will remain set
 * until the queue is released when closing the device node.
 */
void vb2_queue_error(struct vb2_queue *q)
{
        q->error = 1;

        wake_up_all(&q->done_wq);
}
EXPORT_SYMBOL_GPL(vb2_queue_error);

int vb2_core_streamoff(struct vb2_queue *q, unsigned int type)
{
        if (type != q->type) {
                dprintk(1, "invalid stream type\n");
                return -EINVAL;
        }

        /*
         * Cancel will pause streaming and remove all buffers from the driver
         * and videobuf, effectively returning control over them to userspace.
         *
         * Note that we do this even if q->streaming == 0: if you prepare or
         * queue buffers, and then call streamoff without ever having called
         * streamon, you would still expect those buffers to be returned to
         * their normal dequeued state.
         */
        __vb2_queue_cancel(q);
        q->waiting_for_buffers = !q->is_output;
        q->last_buffer_dequeued = false;

        dprintk(3, "successful\n");
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_streamoff);

/**
 * __find_plane_by_offset() - find plane associated with the given offset off
 */
static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
                        unsigned int *_buffer, unsigned int *_plane)
{
        struct vb2_buffer *vb;
        unsigned int buffer, plane;

        /*
         * Go over all buffers and their planes, comparing the given offset
         * with an offset assigned to each plane. If a match is found,
         * return its buffer and plane numbers.
         */
        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
                vb = q->bufs[buffer];

                for (plane = 0; plane < vb->num_planes; ++plane) {
                        if (vb->planes[plane].m.offset == off) {
                                *_buffer = buffer;
                                *_plane = plane;
                                return 0;
                        }
                }
        }

        return -EINVAL;
}

/**
 * vb2_core_expbuf() - Export a buffer as a file descriptor
 * @q:          videobuf2 queue
 * @fd:         file descriptor associated with DMABUF (set by driver) *
 * @type:       buffer type
 * @index:      id number of the buffer
 * @plane:      index of the plane to be exported, 0 for single plane queues
 * @flags:      flags for newly created file, currently only O_CLOEXEC is
 *              supported, refer to manual of open syscall for more details
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_expbuf handler in driver.
 */
int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
                unsigned int index, unsigned int plane, unsigned int flags)
{
        struct vb2_buffer *vb = NULL;
        struct vb2_plane *vb_plane;
        int ret;
        struct dma_buf *dbuf;

        if (q->memory != VB2_MEMORY_MMAP) {
                dprintk(1, "queue is not currently set up for mmap\n");
                return -EINVAL;
        }

        if (!q->mem_ops->get_dmabuf) {
                dprintk(1, "queue does not support DMA buffer exporting\n");
                return -EINVAL;
        }

        if (flags & ~(O_CLOEXEC | O_ACCMODE)) {
                dprintk(1, "queue does support only O_CLOEXEC and access mode flags\n");
                return -EINVAL;
        }

        if (type != q->type) {
                dprintk(1, "invalid buffer type\n");
                return -EINVAL;
        }

        if (index >= q->num_buffers) {
                dprintk(1, "buffer index out of range\n");
                return -EINVAL;
        }

        vb = q->bufs[index];

        if (plane >= vb->num_planes) {
                dprintk(1, "buffer plane out of range\n");
                return -EINVAL;
        }

        if (vb2_fileio_is_active(q)) {
                dprintk(1, "expbuf: file io in progress\n");
                return -EBUSY;
        }

        vb_plane = &vb->planes[plane];

        dbuf = call_ptr_memop(vb, get_dmabuf, vb_plane->mem_priv,
                                flags & O_ACCMODE);
        if (IS_ERR_OR_NULL(dbuf)) {
                dprintk(1, "failed to export buffer %d, plane %d\n",
                        index, plane);
                return -EINVAL;
        }

        ret = dma_buf_fd(dbuf, flags & ~O_ACCMODE);
        if (ret < 0) {
                dprintk(3, "buffer %d, plane %d failed to export (%d)\n",
                        index, plane, ret);
                dma_buf_put(dbuf);
                return ret;
        }

        dprintk(3, "buffer %d, plane %d exported as %d descriptor\n",
                index, plane, ret);
        *fd = ret;

        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_expbuf);

/**
 * vb2_mmap() - map video buffers into application address space
 * @q:          videobuf2 queue
 * @vma:        vma passed to the mmap file operation handler in the driver
 *
 * Should be called from mmap file operation handler of a driver.
 * This function maps one plane of one of the available video buffers to
 * userspace. To map whole video memory allocated on reqbufs, this function
 * has to be called once per each plane per each buffer previously allocated.
 *
 * When the userspace application calls mmap, it passes to it an offset returned
 * to it earlier by the means of vidioc_querybuf handler. That offset acts as
 * a "cookie", which is then used to identify the plane to be mapped.
 * This function finds a plane with a matching offset and a mapping is performed
 * by the means of a provided memory operation.
 *
 * The return values from this function are intended to be directly returned
 * from the mmap handler in driver.
 */
int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
{
        unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
        struct vb2_buffer *vb;
        unsigned int buffer = 0, plane = 0;
        int ret;
        unsigned long length;

        if (q->memory != VB2_MEMORY_MMAP) {
                dprintk(1, "queue is not currently set up for mmap\n");
                return -EINVAL;
        }

        /*
         * Check memory area access mode.
         */
        if (!(vma->vm_flags & VM_SHARED)) {
                dprintk(1, "invalid vma flags, VM_SHARED needed\n");
                return -EINVAL;
        }
        if (q->is_output) {
                if (!(vma->vm_flags & VM_WRITE)) {
                        dprintk(1, "invalid vma flags, VM_WRITE needed\n");
                        return -EINVAL;
                }
        } else {
                if (!(vma->vm_flags & VM_READ)) {
                        dprintk(1, "invalid vma flags, VM_READ needed\n");
                        return -EINVAL;
                }
        }
        if (vb2_fileio_is_active(q)) {
                dprintk(1, "mmap: file io in progress\n");
                return -EBUSY;
        }

        /*
         * Find the plane corresponding to the offset passed by userspace.
         */
        ret = __find_plane_by_offset(q, off, &buffer, &plane);
        if (ret)
                return ret;

        vb = q->bufs[buffer];

        /*
         * MMAP requires page_aligned buffers.
         * The buffer length was page_aligned at __vb2_buf_mem_alloc(),
         * so, we need to do the same here.
         */
        length = PAGE_ALIGN(vb->planes[plane].length);
        if (length < (vma->vm_end - vma->vm_start)) {
                dprintk(1,
                        "MMAP invalid, as it would overflow buffer length\n");
                return -EINVAL;
        }

        mutex_lock(&q->mmap_lock);
        ret = call_memop(vb, mmap, vb->planes[plane].mem_priv, vma);
        mutex_unlock(&q->mmap_lock);
        if (ret)
                return ret;

        dprintk(3, "buffer %d, plane %d successfully mapped\n", buffer, plane);
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_mmap);

#ifndef CONFIG_MMU
unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
                                    unsigned long addr,
                                    unsigned long len,
                                    unsigned long pgoff,
                                    unsigned long flags)
{
        unsigned long off = pgoff << PAGE_SHIFT;
        struct vb2_buffer *vb;
        unsigned int buffer, plane;
        void *vaddr;
        int ret;

        if (q->memory != VB2_MEMORY_MMAP) {
                dprintk(1, "queue is not currently set up for mmap\n");
                return -EINVAL;
        }

        /*
         * Find the plane corresponding to the offset passed by userspace.
         */
        ret = __find_plane_by_offset(q, off, &buffer, &plane);
        if (ret)
                return ret;

        vb = q->bufs[buffer];

        vaddr = vb2_plane_vaddr(vb, plane);
        return vaddr ? (unsigned long)vaddr : -EINVAL;
}
EXPORT_SYMBOL_GPL(vb2_get_unmapped_area);
#endif

/**
 * vb2_core_queue_init() - initialize a videobuf2 queue
 * @q:          videobuf2 queue; this structure should be allocated in driver
 *
 * The vb2_queue structure should be allocated by the driver. The driver is
 * responsible of clearing it's content and setting initial values for some
 * required entries before calling this function.
 * q->ops, q->mem_ops, q->type and q->io_modes are mandatory. Please refer
 * to the struct vb2_queue description in include/media/videobuf2-core.h
 * for more information.
 */
int vb2_core_queue_init(struct vb2_queue *q)
{
        /*
         * Sanity check
         */
        if (WARN_ON(!q)                   ||
            WARN_ON(!q->ops)              ||
            WARN_ON(!q->mem_ops)          ||
            WARN_ON(!q->type)             ||
            WARN_ON(!q->io_modes)         ||
            WARN_ON(!q->ops->queue_setup) ||
            WARN_ON(!q->ops->buf_queue))
                return -EINVAL;

        INIT_LIST_HEAD(&q->queued_list);
        INIT_LIST_HEAD(&q->done_list);
        spin_lock_init(&q->done_lock);
        mutex_init(&q->mmap_lock);
        init_waitqueue_head(&q->done_wq);

        if (q->buf_struct_size == 0)
                q->buf_struct_size = sizeof(struct vb2_buffer);

        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_queue_init);

static int __vb2_init_fileio(struct vb2_queue *q, int read);
static int __vb2_cleanup_fileio(struct vb2_queue *q);
/**
 * vb2_core_queue_release() - stop streaming, release the queue and free memory
 * @q:          videobuf2 queue
 *
 * This function stops streaming and performs necessary clean ups, including
 * freeing video buffer memory. The driver is responsible for freeing
 * the vb2_queue structure itself.
 */
void vb2_core_queue_release(struct vb2_queue *q)
{
        __vb2_cleanup_fileio(q);
        __vb2_queue_cancel(q);
        mutex_lock(&q->mmap_lock);
        __vb2_queue_free(q, q->num_buffers);
        mutex_unlock(&q->mmap_lock);
}
EXPORT_SYMBOL_GPL(vb2_core_queue_release);

/**
 * vb2_core_poll() - implements poll userspace operation
 * @q:          videobuf2 queue
 * @file:       file argument passed to the poll file operation handler
 * @wait:       wait argument passed to the poll file operation handler
 *
 * This function implements poll file operation handler for a driver.
 * For CAPTURE queues, if a buffer is ready to be dequeued, the userspace will
 * be informed that the file descriptor of a video device is available for
 * reading.
 * For OUTPUT queues, if a buffer is ready to be dequeued, the file descriptor
 * will be reported as available for writing.
 *
 * The return values from this function are intended to be directly returned
 * from poll handler in driver.
 */
unsigned int vb2_core_poll(struct vb2_queue *q, struct file *file,
                poll_table *wait)
{
        unsigned long req_events = poll_requested_events(wait);
        struct vb2_buffer *vb = NULL;
        unsigned long flags;

        if (!q->is_output && !(req_events & (POLLIN | POLLRDNORM)))
                return 0;
        if (q->is_output && !(req_events & (POLLOUT | POLLWRNORM)))
                return 0;

        /*
         * Start file I/O emulator only if streaming API has not been used yet.
         */
        if (q->num_buffers == 0 && !vb2_fileio_is_active(q)) {
                if (!q->is_output && (q->io_modes & VB2_READ) &&
                                (req_events & (POLLIN | POLLRDNORM))) {
                        if (__vb2_init_fileio(q, 1))
                                return POLLERR;
                }
                if (q->is_output && (q->io_modes & VB2_WRITE) &&
                                (req_events & (POLLOUT | POLLWRNORM))) {
                        if (__vb2_init_fileio(q, 0))
                                return POLLERR;
                        /*
                         * Write to OUTPUT queue can be done immediately.
                         */
                        return POLLOUT | POLLWRNORM;
                }
        }

        /*
         * There is nothing to wait for if the queue isn't streaming, or if the
         * error flag is set.
         */
        if (!vb2_is_streaming(q) || q->error)
                return POLLERR;

        /*
         * If this quirk is set and QBUF hasn't been called yet then
         * return POLLERR as well. This only affects capture queues, output
         * queues will always initialize waiting_for_buffers to false.
         * This quirk is set by V4L2 for backwards compatibility reasons.
         */
        if (q->quirk_poll_must_check_waiting_for_buffers &&
            q->waiting_for_buffers && (req_events & (POLLIN | POLLRDNORM)))
                return POLLERR;

        /*
         * For output streams you can call write() as long as there are fewer
         * buffers queued than there are buffers available.
         */
        if (q->is_output && q->fileio && q->queued_count < q->num_buffers)
                return POLLOUT | POLLWRNORM;

        if (list_empty(&q->done_list)) {
                /*
                 * If the last buffer was dequeued from a capture queue,
                 * return immediately. DQBUF will return -EPIPE.
                 */
                if (q->last_buffer_dequeued)
                        return POLLIN | POLLRDNORM;

                poll_wait(file, &q->done_wq, wait);
        }

        /*
         * Take first buffer available for dequeuing.
         */
        spin_lock_irqsave(&q->done_lock, flags);
        if (!list_empty(&q->done_list))
                vb = list_first_entry(&q->done_list, struct vb2_buffer,
                                        done_entry);
        spin_unlock_irqrestore(&q->done_lock, flags);

        if (vb && (vb->state == VB2_BUF_STATE_DONE
                        || vb->state == VB2_BUF_STATE_ERROR)) {
                return (q->is_output) ?
                                POLLOUT | POLLWRNORM :
                                POLLIN | POLLRDNORM;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(vb2_core_poll);

/**
 * struct vb2_fileio_buf - buffer context used by file io emulator
 *
 * vb2 provides a compatibility layer and emulator of file io (read and
 * write) calls on top of streaming API. This structure is used for
 * tracking context related to the buffers.
 */
struct vb2_fileio_buf {
        void *vaddr;
        unsigned int size;
        unsigned int pos;
        unsigned int queued:1;
};

/**
 * struct vb2_fileio_data - queue context used by file io emulator
 *
 * @cur_index:  the index of the buffer currently being read from or
 *              written to. If equal to q->num_buffers then a new buffer
 *              must be dequeued.
 * @initial_index: in the read() case all buffers are queued up immediately
 *              in __vb2_init_fileio() and __vb2_perform_fileio() just cycles
 *              buffers. However, in the write() case no buffers are initially
 *              queued, instead whenever a buffer is full it is queued up by
 *              __vb2_perform_fileio(). Only once all available buffers have
 *              been queued up will __vb2_perform_fileio() start to dequeue
 *              buffers. This means that initially __vb2_perform_fileio()
 *              needs to know what buffer index to use when it is queuing up
 *              the buffers for the first time. That initial index is stored
 *              in this field. Once it is equal to q->num_buffers all
 *              available buffers have been queued and __vb2_perform_fileio()
 *              should start the normal dequeue/queue cycle.
 *
 * vb2 provides a compatibility layer and emulator of file io (read and
 * write) calls on top of streaming API. For proper operation it required
 * this structure to save the driver state between each call of the read
 * or write function.
 */
struct vb2_fileio_data {
        unsigned int count;
        unsigned int type;
        unsigned int memory;
        struct vb2_fileio_buf bufs[VB2_MAX_FRAME];
        unsigned int cur_index;
        unsigned int initial_index;
        unsigned int q_count;
        unsigned int dq_count;
        unsigned read_once:1;
        unsigned write_immediately:1;
};

/**
 * __vb2_init_fileio() - initialize file io emulator
 * @q:          videobuf2 queue
 * @read:       mode selector (1 means read, 0 means write)
 */
static int __vb2_init_fileio(struct vb2_queue *q, int read)
{
        struct vb2_fileio_data *fileio;
        int i, ret;
        unsigned int count = 0;

        /*
         * Sanity check
         */
        if (WARN_ON((read && !(q->io_modes & VB2_READ)) ||
                    (!read && !(q->io_modes & VB2_WRITE))))
                return -EINVAL;

        /*
         * Check if device supports mapping buffers to kernel virtual space.
         */
        if (!q->mem_ops->vaddr)
                return -EBUSY;

        /*
         * Check if streaming api has not been already activated.
         */
        if (q->streaming || q->num_buffers > 0)
                return -EBUSY;

        /*
         * Start with count 1, driver can increase it in queue_setup()
         */
        count = 1;

        dprintk(3, "setting up file io: mode %s, count %d, read_once %d, write_immediately %d\n",
                (read) ? "read" : "write", count, q->fileio_read_once,
                q->fileio_write_immediately);

        fileio = kzalloc(sizeof(*fileio), GFP_KERNEL);
        if (fileio == NULL)
                return -ENOMEM;

        fileio->read_once = q->fileio_read_once;
        fileio->write_immediately = q->fileio_write_immediately;

        /*
         * Request buffers and use MMAP type to force driver
         * to allocate buffers by itself.
         */
        fileio->count = count;
        fileio->memory = VB2_MEMORY_MMAP;
        fileio->type = q->type;
        q->fileio = fileio;
        ret = vb2_core_reqbufs(q, fileio->memory, &fileio->count);
        if (ret)
                goto err_kfree;

        /*
         * Check if plane_count is correct
         * (multiplane buffers are not supported).
         */
        if (q->bufs[0]->num_planes != 1) {
                ret = -EBUSY;
                goto err_reqbufs;
        }

        /*
         * Get kernel address of each buffer.
         */
        for (i = 0; i < q->num_buffers; i++) {
                fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
                if (fileio->bufs[i].vaddr == NULL) {
                        ret = -EINVAL;
                        goto err_reqbufs;
                }
                fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
        }

        /*
         * Read mode requires pre queuing of all buffers.
         */
        if (read) {
                /*
                 * Queue all buffers.
                 */
                for (i = 0; i < q->num_buffers; i++) {
                        ret = vb2_core_qbuf(q, i, NULL);
                        if (ret)
                                goto err_reqbufs;
                        fileio->bufs[i].queued = 1;
                }
                /*
                 * All buffers have been queued, so mark that by setting
                 * initial_index to q->num_buffers
                 */
                fileio->initial_index = q->num_buffers;
                fileio->cur_index = q->num_buffers;
        }

        /*
         * Start streaming.
         */
        ret = vb2_core_streamon(q, q->type);
        if (ret)
                goto err_reqbufs;

        return ret;

err_reqbufs:
        fileio->count = 0;
        vb2_core_reqbufs(q, fileio->memory, &fileio->count);

err_kfree:
        q->fileio = NULL;
        kfree(fileio);
        return ret;
}

/**
 * __vb2_cleanup_fileio() - free resourced used by file io emulator
 * @q:          videobuf2 queue
 */
static int __vb2_cleanup_fileio(struct vb2_queue *q)
{
        struct vb2_fileio_data *fileio = q->fileio;

        if (fileio) {
                vb2_core_streamoff(q, q->type);
                q->fileio = NULL;
                fileio->count = 0;
                vb2_core_reqbufs(q, fileio->memory, &fileio->count);
                kfree(fileio);
                dprintk(3, "file io emulator closed\n");
        }
        return 0;
}

/**
 * __vb2_perform_fileio() - perform a single file io (read or write) operation
 * @q:          videobuf2 queue
 * @data:       pointed to target userspace buffer
 * @count:      number of bytes to read or write
 * @ppos:       file handle position tracking pointer
 * @nonblock:   mode selector (1 means blocking calls, 0 means nonblocking)
 * @read:       access mode selector (1 means read, 0 means write)
 */
static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
                loff_t *ppos, int nonblock, int read)
{
        struct vb2_fileio_data *fileio;
        struct vb2_fileio_buf *buf;
        bool is_multiplanar = q->is_multiplanar;
        /*
         * When using write() to write data to an output video node the vb2 core
         * should copy timestamps if V4L2_BUF_FLAG_TIMESTAMP_COPY is set. Nobody
         * else is able to provide this information with the write() operation.
         */
        bool copy_timestamp = !read && q->copy_timestamp;
        unsigned index;
        int ret;

        dprintk(3, "mode %s, offset %ld, count %zd, %sblocking\n",
                read ? "read" : "write", (long)*ppos, count,
                nonblock ? "non" : "");

        if (!data)
                return -EINVAL;

        /*
         * Initialize emulator on first call.
         */
        if (!vb2_fileio_is_active(q)) {
                ret = __vb2_init_fileio(q, read);
                dprintk(3, "vb2_init_fileio result: %d\n", ret);
                if (ret)
                        return ret;
        }
        fileio = q->fileio;

        /*
         * Check if we need to dequeue the buffer.
         */
        index = fileio->cur_index;
        if (index >= q->num_buffers) {
                struct vb2_buffer *b;

                /*
                 * Call vb2_dqbuf to get buffer back.
                 */
                ret = vb2_core_dqbuf(q, &index, NULL, nonblock);
                dprintk(5, "vb2_dqbuf result: %d\n", ret);
                if (ret)
                        return ret;
                fileio->dq_count += 1;

                fileio->cur_index = index;
                buf = &fileio->bufs[index];
                b = q->bufs[index];

                /*
                 * Get number of bytes filled by the driver
                 */
                buf->pos = 0;
                buf->queued = 0;
                buf->size = read ? vb2_get_plane_payload(q->bufs[index], 0)
                                 : vb2_plane_size(q->bufs[index], 0);
                /* Compensate for data_offset on read in the multiplanar case. */
                if (is_multiplanar && read &&
                                b->planes[0].data_offset < buf->size) {
                        buf->pos = b->planes[0].data_offset;
                        buf->size -= buf->pos;
                }
        } else {
                buf = &fileio->bufs[index];
        }

        /*
         * Limit count on last few bytes of the buffer.
         */
        if (buf->pos + count > buf->size) {
                count = buf->size - buf->pos;
                dprintk(5, "reducing read count: %zd\n", count);
        }

        /*
         * Transfer data to userspace.
         */
        dprintk(3, "copying %zd bytes - buffer %d, offset %u\n",
                count, index, buf->pos);
        if (read)
                ret = copy_to_user(data, buf->vaddr + buf->pos, count);
        else
                ret = copy_from_user(buf->vaddr + buf->pos, data, count);
        if (ret) {
                dprintk(3, "error copying data\n");
                return -EFAULT;
        }

        /*
         * Update counters.
         */
        buf->pos += count;
        *ppos += count;

        /*
         * Queue next buffer if required.
         */
        if (buf->pos == buf->size || (!read && fileio->write_immediately)) {
                struct vb2_buffer *b = q->bufs[index];

                /*
                 * Check if this is the last buffer to read.
                 */
                if (read && fileio->read_once && fileio->dq_count == 1) {
                        dprintk(3, "read limit reached\n");
                        return __vb2_cleanup_fileio(q);
                }

                /*
                 * Call vb2_qbuf and give buffer to the driver.
                 */
                b->planes[0].bytesused = buf->pos;

                if (copy_timestamp)
                        b->timestamp = ktime_get_ns();
                ret = vb2_core_qbuf(q, index, NULL);
                dprintk(5, "vb2_dbuf result: %d\n", ret);
                if (ret)
                        return ret;

                /*
                 * Buffer has been queued, update the status
                 */
                buf->pos = 0;
                buf->queued = 1;
                buf->size = vb2_plane_size(q->bufs[index], 0);
                fileio->q_count += 1;
                /*
                 * If we are queuing up buffers for the first time, then
                 * increase initial_index by one.
                 */
                if (fileio->initial_index < q->num_buffers)
                        fileio->initial_index++;
                /*
                 * The next buffer to use is either a buffer that's going to be
                 * queued for the first time (initial_index < q->num_buffers)
                 * or it is equal to q->num_buffers, meaning that the next
                 * time we need to dequeue a buffer since we've now queued up
                 * all the 'first time' buffers.
                 */
                fileio->cur_index = fileio->initial_index;
        }

        /*
         * Return proper number of bytes processed.
         */
        if (ret == 0)
                ret = count;
        return ret;
}

size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
                loff_t *ppos, int nonblocking)
{
        return __vb2_perform_fileio(q, data, count, ppos, nonblocking, 1);
}
EXPORT_SYMBOL_GPL(vb2_read);

size_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
                loff_t *ppos, int nonblocking)
{
        return __vb2_perform_fileio(q, (char __user *) data, count,
                                                        ppos, nonblocking, 0);
}
EXPORT_SYMBOL_GPL(vb2_write);

struct vb2_threadio_data {
        struct task_struct *thread;
        vb2_thread_fnc fnc;
        void *priv;
        bool stop;
};

static int vb2_thread(void *data)
{
        struct vb2_queue *q = data;
        struct vb2_threadio_data *threadio = q->threadio;
        bool copy_timestamp = false;
        unsigned prequeue = 0;
        unsigned index = 0;
        int ret = 0;

        if (q->is_output) {
                prequeue = q->num_buffers;
                copy_timestamp = q->copy_timestamp;
        }

        set_freezable();

        for (;;) {
                struct vb2_buffer *vb;

                /*
                 * Call vb2_dqbuf to get buffer back.
                 */
                if (prequeue) {
                        vb = q->bufs[index++];
                        prequeue--;
                } else {
                        call_void_qop(q, wait_finish, q);
                        if (!threadio->stop)
                                ret = vb2_core_dqbuf(q, &index, NULL, 0);
                        call_void_qop(q, wait_prepare, q);
                        dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
                        if (!ret)
                                vb = q->bufs[index];
                }
                if (ret || threadio->stop)
                        break;
                try_to_freeze();

                if (vb->state != VB2_BUF_STATE_ERROR)
                        if (threadio->fnc(vb, threadio->priv))
                                break;
                call_void_qop(q, wait_finish, q);
                if (copy_timestamp)
                        vb->timestamp = ktime_get_ns();;
                if (!threadio->stop)
                        ret = vb2_core_qbuf(q, vb->index, NULL);
                call_void_qop(q, wait_prepare, q);
                if (ret || threadio->stop)
                        break;
        }

        /* Hmm, linux becomes *very* unhappy without this ... */
        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);
                schedule();
        }
        return 0;
}

/*
 * This function should not be used for anything else but the videobuf2-dvb
 * support. If you think you have another good use-case for this, then please
 * contact the linux-media mailinglist first.
 */
int vb2_thread_start(struct vb2_queue *q, vb2_thread_fnc fnc, void *priv,
                     const char *thread_name)
{
        struct vb2_threadio_data *threadio;
        int ret = 0;

        if (q->threadio)
                return -EBUSY;
        if (vb2_is_busy(q))
                return -EBUSY;
        if (WARN_ON(q->fileio))
                return -EBUSY;

        threadio = kzalloc(sizeof(*threadio), GFP_KERNEL);
        if (threadio == NULL)
                return -ENOMEM;
        threadio->fnc = fnc;
        threadio->priv = priv;

        ret = __vb2_init_fileio(q, !q->is_output);
        dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
        if (ret)
                goto nomem;
        q->threadio = threadio;
        threadio->thread = kthread_run(vb2_thread, q, "vb2-%s", thread_name);
        if (IS_ERR(threadio->thread)) {
                ret = PTR_ERR(threadio->thread);
                threadio->thread = NULL;
                goto nothread;
        }
        return 0;

nothread:
        __vb2_cleanup_fileio(q);
nomem:
        kfree(threadio);
        return ret;
}
EXPORT_SYMBOL_GPL(vb2_thread_start);

int vb2_thread_stop(struct vb2_queue *q)
{
        struct vb2_threadio_data *threadio = q->threadio;
        int err;

        if (threadio == NULL)
                return 0;
        threadio->stop = true;
        /* Wake up all pending sleeps in the thread */
        vb2_queue_error(q);
        err = kthread_stop(threadio->thread);
        __vb2_cleanup_fileio(q);
        threadio->thread = NULL;
        kfree(threadio);
        q->threadio = NULL;
        return err;
}
EXPORT_SYMBOL_GPL(vb2_thread_stop);

MODULE_DESCRIPTION("Media buffer core framework");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>, Marek Szyprowski");
MODULE_LICENSE("GPL");