videobuf-core.c

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/*
 * generic helper functions for handling video4linux capture buffers
 *
 * (c) 2007 Mauro Carvalho Chehab, <[email protected]>
 *
 * Highly based on video-buf written originally by:
 * (c) 2001,02 Gerd Knorr <[email protected]>
 * (c) 2006 Mauro Carvalho Chehab, <[email protected]>
 * (c) 2006 Ted Walther and John Sokol
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/interrupt.h>

#include <media/videobuf-core.h>

#define MAGIC_BUFFER 0x20070728
#define MAGIC_CHECK(is, should)                     \
    do {                                \
        if (unlikely((is) != (should))) {           \
            printk(KERN_ERR                 \
                "magic mismatch: %x (expected %x)\n",   \
                    is, should);            \
            BUG();                      \
        }                           \
    } while (0)

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

MODULE_DESCRIPTION("helper module to manage video4linux buffers");
MODULE_AUTHOR("Mauro Carvalho Chehab <[email protected]>");
MODULE_LICENSE("GPL");

#define dprintk(level, fmt, arg...)                 \
    do {                                \
        if (debug >= level)                 \
            printk(KERN_DEBUG "vbuf: " fmt, ## arg);    \
    } while (0)

/* --------------------------------------------------------------------- */

#define CALL(q, f, arg...)                      \
    ((q->int_ops->f) ? q->int_ops->f(arg) : 0)

struct videobuf_buffer *videobuf_alloc_vb(struct videobuf_queue *q)
{
    struct videobuf_buffer *vb;

    BUG_ON(q->msize < sizeof(*vb));

    if (!q->int_ops || !q->int_ops->alloc_vb) {
        printk(KERN_ERR "No specific ops defined!\n");
        BUG();
    }

    vb = q->int_ops->alloc_vb(q->msize);
    if (NULL != vb) {
        init_waitqueue_head(&vb->done);
        vb->magic = MAGIC_BUFFER;
    }

    return vb;
}
EXPORT_SYMBOL_GPL(videobuf_alloc_vb);

static int is_state_active_or_queued(struct videobuf_queue *q, struct videobuf_buffer *vb)
{
    unsigned long flags;
    bool rc;

    spin_lock_irqsave(q->irqlock, flags);
    rc = vb->state != VIDEOBUF_ACTIVE && vb->state != VIDEOBUF_QUEUED;
    spin_unlock_irqrestore(q->irqlock, flags);
    return rc;
};

int videobuf_waiton(struct videobuf_queue *q, struct videobuf_buffer *vb,
        int non_blocking, int intr)
{
    bool is_ext_locked;
    int ret = 0;

    MAGIC_CHECK(vb->magic, MAGIC_BUFFER);

    if (non_blocking) {
        if (is_state_active_or_queued(q, vb))
            return 0;
        return -EAGAIN;
    }

    is_ext_locked = q->ext_lock && mutex_is_locked(q->ext_lock);

    /* Release vdev lock to prevent this wait from blocking outside access to
       the device. */
    if (is_ext_locked)
        mutex_unlock(q->ext_lock);
    if (intr)
        ret = wait_event_interruptible(vb->done, is_state_active_or_queued(q, vb));
    else
        wait_event(vb->done, is_state_active_or_queued(q, vb));
    /* Relock */
    if (is_ext_locked)
        mutex_lock(q->ext_lock);

    return ret;
}
EXPORT_SYMBOL_GPL(videobuf_waiton);

int videobuf_iolock(struct videobuf_queue *q, struct videobuf_buffer *vb,
            struct v4l2_framebuffer *fbuf)
{
    MAGIC_CHECK(vb->magic, MAGIC_BUFFER);
    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    return CALL(q, iolock, q, vb, fbuf);
}
EXPORT_SYMBOL_GPL(videobuf_iolock);

void *videobuf_queue_to_vaddr(struct videobuf_queue *q,
                  struct videobuf_buffer *buf)
{
    if (q->int_ops->vaddr)
        return q->int_ops->vaddr(buf);
    return NULL;
}
EXPORT_SYMBOL_GPL(videobuf_queue_to_vaddr);

/* --------------------------------------------------------------------- */


void videobuf_queue_core_init(struct videobuf_queue *q,
             const struct videobuf_queue_ops *ops,
             struct device *dev,
             spinlock_t *irqlock,
             enum v4l2_buf_type type,
             enum v4l2_field field,
             unsigned int msize,
             void *priv,
             struct videobuf_qtype_ops *int_ops,
             struct mutex *ext_lock)
{
    BUG_ON(!q);
    memset(q, 0, sizeof(*q));
    q->irqlock   = irqlock;
    q->ext_lock  = ext_lock;
    q->dev       = dev;
    q->type      = type;
    q->field     = field;
    q->msize     = msize;
    q->ops       = ops;
    q->priv_data = priv;
    q->int_ops   = int_ops;

    /* All buffer operations are mandatory */
    BUG_ON(!q->ops->buf_setup);
    BUG_ON(!q->ops->buf_prepare);
    BUG_ON(!q->ops->buf_queue);
    BUG_ON(!q->ops->buf_release);

    /* Lock is mandatory for queue_cancel to work */
    BUG_ON(!irqlock);

    /* Having implementations for abstract methods are mandatory */
    BUG_ON(!q->int_ops);

    mutex_init(&q->vb_lock);
    init_waitqueue_head(&q->wait);
    INIT_LIST_HEAD(&q->stream);
}
EXPORT_SYMBOL_GPL(videobuf_queue_core_init);

/* Locking: Only usage in bttv unsafe find way to remove */
int videobuf_queue_is_busy(struct videobuf_queue *q)
{
    int i;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    if (q->streaming) {
        dprintk(1, "busy: streaming active\n");
        return 1;
    }
    if (q->reading) {
        dprintk(1, "busy: pending read #1\n");
        return 1;
    }
    if (q->read_buf) {
        dprintk(1, "busy: pending read #2\n");
        return 1;
    }
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        if (NULL == q->bufs[i])
            continue;
        if (q->bufs[i]->map) {
            dprintk(1, "busy: buffer #%d mapped\n", i);
            return 1;
        }
        if (q->bufs[i]->state == VIDEOBUF_QUEUED) {
            dprintk(1, "busy: buffer #%d queued\n", i);
            return 1;
        }
        if (q->bufs[i]->state == VIDEOBUF_ACTIVE) {
            dprintk(1, "busy: buffer #%d avtive\n", i);
            return 1;
        }
    }
    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_queue_is_busy);

/* Locking: Caller holds q->vb_lock */
static int __videobuf_free(struct videobuf_queue *q)
{
    int i;

    dprintk(1, "%s\n", __func__);
    if (!q)
        return 0;

    if (q->streaming || q->reading) {
        dprintk(1, "Cannot free buffers when streaming or reading\n");
        return -EBUSY;
    }

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    for (i = 0; i < VIDEO_MAX_FRAME; i++)
        if (q->bufs[i] && q->bufs[i]->map) {
            dprintk(1, "Cannot free mmapped buffers\n");
            return -EBUSY;
        }

    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        if (NULL == q->bufs[i])
            continue;
        q->ops->buf_release(q, q->bufs[i]);
        kfree(q->bufs[i]);
        q->bufs[i] = NULL;
    }

    return 0;
}

/* Locking: Caller holds q->vb_lock */
void videobuf_queue_cancel(struct videobuf_queue *q)
{
    unsigned long flags = 0;
    int i;

    q->streaming = 0;
    q->reading  = 0;
    wake_up_interruptible_sync(&q->wait);

    /* remove queued buffers from list */
    spin_lock_irqsave(q->irqlock, flags);
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        if (NULL == q->bufs[i])
            continue;
        if (q->bufs[i]->state == VIDEOBUF_QUEUED) {
            list_del(&q->bufs[i]->queue);
            q->bufs[i]->state = VIDEOBUF_ERROR;
            wake_up_all(&q->bufs[i]->done);
        }
    }
    spin_unlock_irqrestore(q->irqlock, flags);

    /* free all buffers + clear queue */
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        if (NULL == q->bufs[i])
            continue;
        q->ops->buf_release(q, q->bufs[i]);
    }
    INIT_LIST_HEAD(&q->stream);
}
EXPORT_SYMBOL_GPL(videobuf_queue_cancel);

/* --------------------------------------------------------------------- */

/* Locking: Caller holds q->vb_lock */
enum v4l2_field videobuf_next_field(struct videobuf_queue *q)
{
    enum v4l2_field field = q->field;

    BUG_ON(V4L2_FIELD_ANY == field);

    if (V4L2_FIELD_ALTERNATE == field) {
        if (V4L2_FIELD_TOP == q->last) {
            field   = V4L2_FIELD_BOTTOM;
            q->last = V4L2_FIELD_BOTTOM;
        } else {
            field   = V4L2_FIELD_TOP;
            q->last = V4L2_FIELD_TOP;
        }
    }
    return field;
}
EXPORT_SYMBOL_GPL(videobuf_next_field);

/* Locking: Caller holds q->vb_lock */
static void videobuf_status(struct videobuf_queue *q, struct v4l2_buffer *b,
                struct videobuf_buffer *vb, enum v4l2_buf_type type)
{
    MAGIC_CHECK(vb->magic, MAGIC_BUFFER);
    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    b->index    = vb->i;
    b->type     = type;

    b->memory   = vb->memory;
    switch (b->memory) {
    case V4L2_MEMORY_MMAP:
        b->m.offset  = vb->boff;
        b->length    = vb->bsize;
        break;
    case V4L2_MEMORY_USERPTR:
        b->m.userptr = vb->baddr;
        b->length    = vb->bsize;
        break;
    case V4L2_MEMORY_OVERLAY:
        b->m.offset  = vb->boff;
        break;
    }

    b->flags    = 0;
    if (vb->map)
        b->flags |= V4L2_BUF_FLAG_MAPPED;

    switch (vb->state) {
    case VIDEOBUF_PREPARED:
    case VIDEOBUF_QUEUED:
    case VIDEOBUF_ACTIVE:
        b->flags |= V4L2_BUF_FLAG_QUEUED;
        break;
    case VIDEOBUF_ERROR:
        b->flags |= V4L2_BUF_FLAG_ERROR;
        /* fall through */
    case VIDEOBUF_DONE:
        b->flags |= V4L2_BUF_FLAG_DONE;
        break;
    case VIDEOBUF_NEEDS_INIT:
    case VIDEOBUF_IDLE:
        /* nothing */
        break;
    }

    b->field     = vb->field;
    b->timestamp = vb->ts;
    b->bytesused = vb->size;
    b->sequence  = vb->field_count >> 1;
}

int videobuf_mmap_free(struct videobuf_queue *q)
{
    int ret;
    videobuf_queue_lock(q);
    ret = __videobuf_free(q);
    videobuf_queue_unlock(q);
    return ret;
}
EXPORT_SYMBOL_GPL(videobuf_mmap_free);

/* Locking: Caller holds q->vb_lock */
int __videobuf_mmap_setup(struct videobuf_queue *q,
            unsigned int bcount, unsigned int bsize,
            enum v4l2_memory memory)
{
    unsigned int i;
    int err;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    err = __videobuf_free(q);
    if (0 != err)
        return err;

    /* Allocate and initialize buffers */
    for (i = 0; i < bcount; i++) {
        q->bufs[i] = videobuf_alloc_vb(q);

        if (NULL == q->bufs[i])
            break;

        q->bufs[i]->i      = i;
        q->bufs[i]->memory = memory;
        q->bufs[i]->bsize  = bsize;
        switch (memory) {
        case V4L2_MEMORY_MMAP:
            q->bufs[i]->boff = PAGE_ALIGN(bsize) * i;
            break;
        case V4L2_MEMORY_USERPTR:
        case V4L2_MEMORY_OVERLAY:
            /* nothing */
            break;
        }
    }

    if (!i)
        return -ENOMEM;

    dprintk(1, "mmap setup: %d buffers, %d bytes each\n", i, bsize);

    return i;
}
EXPORT_SYMBOL_GPL(__videobuf_mmap_setup);

int videobuf_mmap_setup(struct videobuf_queue *q,
            unsigned int bcount, unsigned int bsize,
            enum v4l2_memory memory)
{
    int ret;
    videobuf_queue_lock(q);
    ret = __videobuf_mmap_setup(q, bcount, bsize, memory);
    videobuf_queue_unlock(q);
    return ret;
}
EXPORT_SYMBOL_GPL(videobuf_mmap_setup);

int videobuf_reqbufs(struct videobuf_queue *q,
         struct v4l2_requestbuffers *req)
{
    unsigned int size, count;
    int retval;

    if (req->count < 1) {
        dprintk(1, "reqbufs: count invalid (%d)\n", req->count);
        return -EINVAL;
    }

    if (req->memory != V4L2_MEMORY_MMAP     &&
        req->memory != V4L2_MEMORY_USERPTR  &&
        req->memory != V4L2_MEMORY_OVERLAY) {
        dprintk(1, "reqbufs: memory type invalid\n");
        return -EINVAL;
    }

    videobuf_queue_lock(q);
    if (req->type != q->type) {
        dprintk(1, "reqbufs: queue type invalid\n");
        retval = -EINVAL;
        goto done;
    }

    if (q->streaming) {
        dprintk(1, "reqbufs: streaming already exists\n");
        retval = -EBUSY;
        goto done;
    }
    if (!list_empty(&q->stream)) {
        dprintk(1, "reqbufs: stream running\n");
        retval = -EBUSY;
        goto done;
    }

    count = req->count;
    if (count > VIDEO_MAX_FRAME)
        count = VIDEO_MAX_FRAME;
    size = 0;
    q->ops->buf_setup(q, &count, &size);
    dprintk(1, "reqbufs: bufs=%d, size=0x%x [%u pages total]\n",
        count, size,
        (unsigned int)((count * PAGE_ALIGN(size)) >> PAGE_SHIFT));

    retval = __videobuf_mmap_setup(q, count, size, req->memory);
    if (retval < 0) {
        dprintk(1, "reqbufs: mmap setup returned %d\n", retval);
        goto done;
    }

    req->count = retval;
    retval = 0;

 done:
    videobuf_queue_unlock(q);
    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_reqbufs);

int videobuf_querybuf(struct videobuf_queue *q, struct v4l2_buffer *b)
{
    int ret = -EINVAL;

    videobuf_queue_lock(q);
    if (unlikely(b->type != q->type)) {
        dprintk(1, "querybuf: Wrong type.\n");
        goto done;
    }
    if (unlikely(b->index >= VIDEO_MAX_FRAME)) {
        dprintk(1, "querybuf: index out of range.\n");
        goto done;
    }
    if (unlikely(NULL == q->bufs[b->index])) {
        dprintk(1, "querybuf: buffer is null.\n");
        goto done;
    }

    videobuf_status(q, b, q->bufs[b->index], q->type);

    ret = 0;
done:
    videobuf_queue_unlock(q);
    return ret;
}
EXPORT_SYMBOL_GPL(videobuf_querybuf);

int videobuf_qbuf(struct videobuf_queue *q, struct v4l2_buffer *b)
{
    struct videobuf_buffer *buf;
    enum v4l2_field field;
    unsigned long flags = 0;
    int retval;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    if (b->memory == V4L2_MEMORY_MMAP)
        down_read(&current->mm->mmap_sem);

    videobuf_queue_lock(q);
    retval = -EBUSY;
    if (q->reading) {
        dprintk(1, "qbuf: Reading running...\n");
        goto done;
    }
    retval = -EINVAL;
    if (b->type != q->type) {
        dprintk(1, "qbuf: Wrong type.\n");
        goto done;
    }
    if (b->index >= VIDEO_MAX_FRAME) {
        dprintk(1, "qbuf: index out of range.\n");
        goto done;
    }
    buf = q->bufs[b->index];
    if (NULL == buf) {
        dprintk(1, "qbuf: buffer is null.\n");
        goto done;
    }
    MAGIC_CHECK(buf->magic, MAGIC_BUFFER);
    if (buf->memory != b->memory) {
        dprintk(1, "qbuf: memory type is wrong.\n");
        goto done;
    }
    if (buf->state != VIDEOBUF_NEEDS_INIT && buf->state != VIDEOBUF_IDLE) {
        dprintk(1, "qbuf: buffer is already queued or active.\n");
        goto done;
    }

    switch (b->memory) {
    case V4L2_MEMORY_MMAP:
        if (0 == buf->baddr) {
            dprintk(1, "qbuf: mmap requested "
                   "but buffer addr is zero!\n");
            goto done;
        }
        if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT
            || q->type == V4L2_BUF_TYPE_VBI_OUTPUT
            || q->type == V4L2_BUF_TYPE_SLICED_VBI_OUTPUT) {
            buf->size = b->bytesused;
            buf->field = b->field;
            buf->ts = b->timestamp;
        }
        break;
    case V4L2_MEMORY_USERPTR:
        if (b->length < buf->bsize) {
            dprintk(1, "qbuf: buffer length is not enough\n");
            goto done;
        }
        if (VIDEOBUF_NEEDS_INIT != buf->state &&
            buf->baddr != b->m.userptr)
            q->ops->buf_release(q, buf);
        buf->baddr = b->m.userptr;
        break;
    case V4L2_MEMORY_OVERLAY:
        buf->boff = b->m.offset;
        break;
    default:
        dprintk(1, "qbuf: wrong memory type\n");
        goto done;
    }

    dprintk(1, "qbuf: requesting next field\n");
    field = videobuf_next_field(q);
    retval = q->ops->buf_prepare(q, buf, field);
    if (0 != retval) {
        dprintk(1, "qbuf: buffer_prepare returned %d\n", retval);
        goto done;
    }

    list_add_tail(&buf->stream, &q->stream);
    if (q->streaming) {
        spin_lock_irqsave(q->irqlock, flags);
        q->ops->buf_queue(q, buf);
        spin_unlock_irqrestore(q->irqlock, flags);
    }
    dprintk(1, "qbuf: succeeded\n");
    retval = 0;
    wake_up_interruptible_sync(&q->wait);

done:
    videobuf_queue_unlock(q);

    if (b->memory == V4L2_MEMORY_MMAP)
        up_read(&current->mm->mmap_sem);

    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_qbuf);

/* Locking: Caller holds q->vb_lock */
static int stream_next_buffer_check_queue(struct videobuf_queue *q, int noblock)
{
    int retval;

checks:
    if (!q->streaming) {
        dprintk(1, "next_buffer: Not streaming\n");
        retval = -EINVAL;
        goto done;
    }

    if (list_empty(&q->stream)) {
        if (noblock) {
            retval = -EAGAIN;
            dprintk(2, "next_buffer: no buffers to dequeue\n");
            goto done;
        } else {
            dprintk(2, "next_buffer: waiting on buffer\n");

            /* Drop lock to avoid deadlock with qbuf */
            videobuf_queue_unlock(q);

            /* Checking list_empty and streaming is safe without
             * locks because we goto checks to validate while
             * holding locks before proceeding */
            retval = wait_event_interruptible(q->wait,
                !list_empty(&q->stream) || !q->streaming);
            videobuf_queue_lock(q);

            if (retval)
                goto done;

            goto checks;
        }
    }

    retval = 0;

done:
    return retval;
}

/* Locking: Caller holds q->vb_lock */
static int stream_next_buffer(struct videobuf_queue *q,
            struct videobuf_buffer **vb, int nonblocking)
{
    int retval;
    struct videobuf_buffer *buf = NULL;

    retval = stream_next_buffer_check_queue(q, nonblocking);
    if (retval)
        goto done;

    buf = list_entry(q->stream.next, struct videobuf_buffer, stream);
    retval = videobuf_waiton(q, buf, nonblocking, 1);
    if (retval < 0)
        goto done;

    *vb = buf;
done:
    return retval;
}

int videobuf_dqbuf(struct videobuf_queue *q,
           struct v4l2_buffer *b, int nonblocking)
{
    struct videobuf_buffer *buf = NULL;
    int retval;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    memset(b, 0, sizeof(*b));
    videobuf_queue_lock(q);

    retval = stream_next_buffer(q, &buf, nonblocking);
    if (retval < 0) {
        dprintk(1, "dqbuf: next_buffer error: %i\n", retval);
        goto done;
    }

    switch (buf->state) {
    case VIDEOBUF_ERROR:
        dprintk(1, "dqbuf: state is error\n");
        break;
    case VIDEOBUF_DONE:
        dprintk(1, "dqbuf: state is done\n");
        break;
    default:
        dprintk(1, "dqbuf: state invalid\n");
        retval = -EINVAL;
        goto done;
    }
    CALL(q, sync, q, buf);
    videobuf_status(q, b, buf, q->type);
    list_del(&buf->stream);
    buf->state = VIDEOBUF_IDLE;
    b->flags &= ~V4L2_BUF_FLAG_DONE;
done:
    videobuf_queue_unlock(q);
    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_dqbuf);

int videobuf_streamon(struct videobuf_queue *q)
{
    struct videobuf_buffer *buf;
    unsigned long flags = 0;
    int retval;

    videobuf_queue_lock(q);
    retval = -EBUSY;
    if (q->reading)
        goto done;
    retval = 0;
    if (q->streaming)
        goto done;
    q->streaming = 1;
    spin_lock_irqsave(q->irqlock, flags);
    list_for_each_entry(buf, &q->stream, stream)
        if (buf->state == VIDEOBUF_PREPARED)
            q->ops->buf_queue(q, buf);
    spin_unlock_irqrestore(q->irqlock, flags);

    wake_up_interruptible_sync(&q->wait);
done:
    videobuf_queue_unlock(q);
    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_streamon);

/* Locking: Caller holds q->vb_lock */
static int __videobuf_streamoff(struct videobuf_queue *q)
{
    if (!q->streaming)
        return -EINVAL;

    videobuf_queue_cancel(q);

    return 0;
}

int videobuf_streamoff(struct videobuf_queue *q)
{
    int retval;

    videobuf_queue_lock(q);
    retval = __videobuf_streamoff(q);
    videobuf_queue_unlock(q);

    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_streamoff);

/* Locking: Caller holds q->vb_lock */
static ssize_t videobuf_read_zerocopy(struct videobuf_queue *q,
                      char __user *data,
                      size_t count, loff_t *ppos)
{
    enum v4l2_field field;
    unsigned long flags = 0;
    int retval;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    /* setup stuff */
    q->read_buf = videobuf_alloc_vb(q);
    if (NULL == q->read_buf)
        return -ENOMEM;

    q->read_buf->memory = V4L2_MEMORY_USERPTR;
    q->read_buf->baddr  = (unsigned long)data;
    q->read_buf->bsize  = count;

    field = videobuf_next_field(q);
    retval = q->ops->buf_prepare(q, q->read_buf, field);
    if (0 != retval)
        goto done;

    /* start capture & wait */
    spin_lock_irqsave(q->irqlock, flags);
    q->ops->buf_queue(q, q->read_buf);
    spin_unlock_irqrestore(q->irqlock, flags);
    retval = videobuf_waiton(q, q->read_buf, 0, 0);
    if (0 == retval) {
        CALL(q, sync, q, q->read_buf);
        if (VIDEOBUF_ERROR == q->read_buf->state)
            retval = -EIO;
        else
            retval = q->read_buf->size;
    }

done:
    /* cleanup */
    q->ops->buf_release(q, q->read_buf);
    kfree(q->read_buf);
    q->read_buf = NULL;
    return retval;
}

static int __videobuf_copy_to_user(struct videobuf_queue *q,
                   struct videobuf_buffer *buf,
                   char __user *data, size_t count,
                   int nonblocking)
{
    void *vaddr = CALL(q, vaddr, buf);

    /* copy to userspace */
    if (count > buf->size - q->read_off)
        count = buf->size - q->read_off;

    if (copy_to_user(data, vaddr + q->read_off, count))
        return -EFAULT;

    return count;
}

static int __videobuf_copy_stream(struct videobuf_queue *q,
                  struct videobuf_buffer *buf,
                  char __user *data, size_t count, size_t pos,
                  int vbihack, int nonblocking)
{
    unsigned int *fc = CALL(q, vaddr, buf);

    if (vbihack) {
        /* dirty, undocumented hack -- pass the frame counter
            * within the last four bytes of each vbi data block.
            * We need that one to maintain backward compatibility
            * to all vbi decoding software out there ... */
        fc += (buf->size >> 2) - 1;
        *fc = buf->field_count >> 1;
        dprintk(1, "vbihack: %d\n", *fc);
    }

    /* copy stuff using the common method */
    count = __videobuf_copy_to_user(q, buf, data, count, nonblocking);

    if ((count == -EFAULT) && (pos == 0))
        return -EFAULT;

    return count;
}

ssize_t videobuf_read_one(struct videobuf_queue *q,
              char __user *data, size_t count, loff_t *ppos,
              int nonblocking)
{
    enum v4l2_field field;
    unsigned long flags = 0;
    unsigned size = 0, nbufs = 1;
    int retval;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    videobuf_queue_lock(q);

    q->ops->buf_setup(q, &nbufs, &size);

    if (NULL == q->read_buf  &&
        count >= size        &&
        !nonblocking) {
        retval = videobuf_read_zerocopy(q, data, count, ppos);
        if (retval >= 0  ||  retval == -EIO)
            /* ok, all done */
            goto done;
        /* fallback to kernel bounce buffer on failures */
    }

    if (NULL == q->read_buf) {
        /* need to capture a new frame */
        retval = -ENOMEM;
        q->read_buf = videobuf_alloc_vb(q);

        dprintk(1, "video alloc=0x%p\n", q->read_buf);
        if (NULL == q->read_buf)
            goto done;
        q->read_buf->memory = V4L2_MEMORY_USERPTR;
        q->read_buf->bsize = count; /* preferred size */
        field = videobuf_next_field(q);
        retval = q->ops->buf_prepare(q, q->read_buf, field);

        if (0 != retval) {
            kfree(q->read_buf);
            q->read_buf = NULL;
            goto done;
        }

        spin_lock_irqsave(q->irqlock, flags);
        q->ops->buf_queue(q, q->read_buf);
        spin_unlock_irqrestore(q->irqlock, flags);

        q->read_off = 0;
    }

    /* wait until capture is done */
    retval = videobuf_waiton(q, q->read_buf, nonblocking, 1);
    if (0 != retval)
        goto done;

    CALL(q, sync, q, q->read_buf);

    if (VIDEOBUF_ERROR == q->read_buf->state) {
        /* catch I/O errors */
        q->ops->buf_release(q, q->read_buf);
        kfree(q->read_buf);
        q->read_buf = NULL;
        retval = -EIO;
        goto done;
    }

    /* Copy to userspace */
    retval = __videobuf_copy_to_user(q, q->read_buf, data, count, nonblocking);
    if (retval < 0)
        goto done;

    q->read_off += retval;
    if (q->read_off == q->read_buf->size) {
        /* all data copied, cleanup */
        q->ops->buf_release(q, q->read_buf);
        kfree(q->read_buf);
        q->read_buf = NULL;
    }

done:
    videobuf_queue_unlock(q);
    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_read_one);

/* Locking: Caller holds q->vb_lock */
static int __videobuf_read_start(struct videobuf_queue *q)
{
    enum v4l2_field field;
    unsigned long flags = 0;
    unsigned int count = 0, size = 0;
    int err, i;

    q->ops->buf_setup(q, &count, &size);
    if (count < 2)
        count = 2;
    if (count > VIDEO_MAX_FRAME)
        count = VIDEO_MAX_FRAME;
    size = PAGE_ALIGN(size);

    err = __videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
    if (err < 0)
        return err;

    count = err;

    for (i = 0; i < count; i++) {
        field = videobuf_next_field(q);
        err = q->ops->buf_prepare(q, q->bufs[i], field);
        if (err)
            return err;
        list_add_tail(&q->bufs[i]->stream, &q->stream);
    }
    spin_lock_irqsave(q->irqlock, flags);
    for (i = 0; i < count; i++)
        q->ops->buf_queue(q, q->bufs[i]);
    spin_unlock_irqrestore(q->irqlock, flags);
    q->reading = 1;
    return 0;
}

static void __videobuf_read_stop(struct videobuf_queue *q)
{
    int i;

    videobuf_queue_cancel(q);
    __videobuf_free(q);
    INIT_LIST_HEAD(&q->stream);
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        if (NULL == q->bufs[i])
            continue;
        kfree(q->bufs[i]);
        q->bufs[i] = NULL;
    }
    q->read_buf = NULL;
}

int videobuf_read_start(struct videobuf_queue *q)
{
    int rc;

    videobuf_queue_lock(q);
    rc = __videobuf_read_start(q);
    videobuf_queue_unlock(q);

    return rc;
}
EXPORT_SYMBOL_GPL(videobuf_read_start);

void videobuf_read_stop(struct videobuf_queue *q)
{
    videobuf_queue_lock(q);
    __videobuf_read_stop(q);
    videobuf_queue_unlock(q);
}
EXPORT_SYMBOL_GPL(videobuf_read_stop);

void videobuf_stop(struct videobuf_queue *q)
{
    videobuf_queue_lock(q);

    if (q->streaming)
        __videobuf_streamoff(q);

    if (q->reading)
        __videobuf_read_stop(q);

    videobuf_queue_unlock(q);
}
EXPORT_SYMBOL_GPL(videobuf_stop);

ssize_t videobuf_read_stream(struct videobuf_queue *q,
                 char __user *data, size_t count, loff_t *ppos,
                 int vbihack, int nonblocking)
{
    int rc, retval;
    unsigned long flags = 0;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    dprintk(2, "%s\n", __func__);
    videobuf_queue_lock(q);
    retval = -EBUSY;
    if (q->streaming)
        goto done;
    if (!q->reading) {
        retval = __videobuf_read_start(q);
        if (retval < 0)
            goto done;
    }

    retval = 0;
    while (count > 0) {
        /* get / wait for data */
        if (NULL == q->read_buf) {
            q->read_buf = list_entry(q->stream.next,
                         struct videobuf_buffer,
                         stream);
            list_del(&q->read_buf->stream);
            q->read_off = 0;
        }
        rc = videobuf_waiton(q, q->read_buf, nonblocking, 1);
        if (rc < 0) {
            if (0 == retval)
                retval = rc;
            break;
        }

        if (q->read_buf->state == VIDEOBUF_DONE) {
            rc = __videobuf_copy_stream(q, q->read_buf, data + retval, count,
                    retval, vbihack, nonblocking);
            if (rc < 0) {
                retval = rc;
                break;
            }
            retval      += rc;
            count       -= rc;
            q->read_off += rc;
        } else {
            /* some error */
            q->read_off = q->read_buf->size;
            if (0 == retval)
                retval = -EIO;
        }

        /* requeue buffer when done with copying */
        if (q->read_off == q->read_buf->size) {
            list_add_tail(&q->read_buf->stream,
                      &q->stream);
            spin_lock_irqsave(q->irqlock, flags);
            q->ops->buf_queue(q, q->read_buf);
            spin_unlock_irqrestore(q->irqlock, flags);
            q->read_buf = NULL;
        }
        if (retval < 0)
            break;
    }

done:
    videobuf_queue_unlock(q);
    return retval;
}
EXPORT_SYMBOL_GPL(videobuf_read_stream);

unsigned int videobuf_poll_stream(struct file *file,
                  struct videobuf_queue *q,
                  poll_table *wait)
{
    unsigned long req_events = poll_requested_events(wait);
    struct videobuf_buffer *buf = NULL;
    unsigned int rc = 0;

    videobuf_queue_lock(q);
    if (q->streaming) {
        if (!list_empty(&q->stream))
            buf = list_entry(q->stream.next,
                     struct videobuf_buffer, stream);
    } else if (req_events & (POLLIN | POLLRDNORM)) {
        if (!q->reading)
            __videobuf_read_start(q);
        if (!q->reading) {
            rc = POLLERR;
        } else if (NULL == q->read_buf) {
            q->read_buf = list_entry(q->stream.next,
                         struct videobuf_buffer,
                         stream);
            list_del(&q->read_buf->stream);
            q->read_off = 0;
        }
        buf = q->read_buf;
    }
    if (!buf)
        rc = POLLERR;

    if (0 == rc) {
        poll_wait(file, &buf->done, wait);
        if (buf->state == VIDEOBUF_DONE ||
            buf->state == VIDEOBUF_ERROR) {
            switch (q->type) {
            case V4L2_BUF_TYPE_VIDEO_OUTPUT:
            case V4L2_BUF_TYPE_VBI_OUTPUT:
            case V4L2_BUF_TYPE_SLICED_VBI_OUTPUT:
                rc = POLLOUT | POLLWRNORM;
                break;
            default:
                rc = POLLIN | POLLRDNORM;
                break;
            }
        }
    }
    videobuf_queue_unlock(q);
    return rc;
}
EXPORT_SYMBOL_GPL(videobuf_poll_stream);

int videobuf_mmap_mapper(struct videobuf_queue *q, struct vm_area_struct *vma)
{
    int rc = -EINVAL;
    int i;

    MAGIC_CHECK(q->int_ops->magic, MAGIC_QTYPE_OPS);

    if (!(vma->vm_flags & VM_WRITE) || !(vma->vm_flags & VM_SHARED)) {
        dprintk(1, "mmap appl bug: PROT_WRITE and MAP_SHARED are required\n");
        return -EINVAL;
    }

    videobuf_queue_lock(q);
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {
        struct videobuf_buffer *buf = q->bufs[i];

        if (buf && buf->memory == V4L2_MEMORY_MMAP &&
                buf->boff == (vma->vm_pgoff << PAGE_SHIFT)) {
            rc = CALL(q, mmap_mapper, q, buf, vma);
            break;
        }
    }
    videobuf_queue_unlock(q);

    return rc;
}
EXPORT_SYMBOL_GPL(videobuf_mmap_mapper);