videobuf2-core.c

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/*
 * videobuf2-core.c - V4L2 driver helper framework
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <[email protected]>
 *     Marek Szyprowski <[email protected]>
 *
 * 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 <media/v4l2-dev.h>
#include <media/v4l2-fh.h>
#include <media/v4l2-event.h>
#include <media/videobuf2-core.h>

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

#define dprintk(level, fmt, arg...)                 \
    do {                                \
        if (debug >= level)                 \
            printk(KERN_DEBUG "vb2: " fmt, ## arg);     \
    } while (0)

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

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

#define V4L2_BUFFER_STATE_FLAGS (V4L2_BUF_FLAG_MAPPED | V4L2_BUF_FLAG_QUEUED | \
                 V4L2_BUF_FLAG_DONE | V4L2_BUF_FLAG_ERROR | \
                 V4L2_BUF_FLAG_PREPARED)

static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
{
    struct vb2_queue *q = vb->vb2_queue;
    void *mem_priv;
    int plane;

    /* Allocate memory for all planes in this buffer */
    for (plane = 0; plane < vb->num_planes; ++plane) {
        mem_priv = call_memop(q, alloc, q->alloc_ctx[plane],
                      q->plane_sizes[plane]);
        if (IS_ERR_OR_NULL(mem_priv))
            goto free;

        /* Associate allocator private data with this plane */
        vb->planes[plane].mem_priv = mem_priv;
        vb->v4l2_planes[plane].length = q->plane_sizes[plane];
    }

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

    return -ENOMEM;
}

static void __vb2_buf_mem_free(struct vb2_buffer *vb)
{
    struct vb2_queue *q = vb->vb2_queue;
    unsigned int plane;

    for (plane = 0; plane < vb->num_planes; ++plane) {
        call_memop(q, put, vb->planes[plane].mem_priv);
        vb->planes[plane].mem_priv = NULL;
        dprintk(3, "Freed plane %d of buffer %d\n", plane,
            vb->v4l2_buf.index);
    }
}

static void __vb2_buf_userptr_put(struct vb2_buffer *vb)
{
    struct vb2_queue *q = vb->vb2_queue;
    unsigned int plane;

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

static void __setup_offsets(struct vb2_queue *q, unsigned int n)
{
    unsigned int buffer, plane;
    struct vb2_buffer *vb;
    unsigned long off;

    if (q->num_buffers) {
        struct v4l2_plane *p;
        vb = q->bufs[q->num_buffers - 1];
        p = &vb->v4l2_planes[vb->num_planes - 1];
        off = PAGE_ALIGN(p->m.mem_offset + p->length);
    } else {
        off = 0;
    }

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

        for (plane = 0; plane < vb->num_planes; ++plane) {
            vb->v4l2_planes[plane].length = q->plane_sizes[plane];
            vb->v4l2_planes[plane].m.mem_offset = off;

            dprintk(3, "Buffer %d, plane %d offset 0x%08lx\n",
                    buffer, plane, off);

            off += vb->v4l2_planes[plane].length;
            off = PAGE_ALIGN(off);
        }
    }
}

static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory,
                 unsigned int num_buffers, unsigned int num_planes)
{
    unsigned int buffer;
    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;
        }

        /* Length stores number of planes for multiplanar buffers */
        if (V4L2_TYPE_IS_MULTIPLANAR(q->type))
            vb->v4l2_buf.length = num_planes;

        vb->state = VB2_BUF_STATE_DEQUEUED;
        vb->vb2_queue = q;
        vb->num_planes = num_planes;
        vb->v4l2_buf.index = q->num_buffers + buffer;
        vb->v4l2_buf.type = q->type;
        vb->v4l2_buf.memory = memory;

        /* Allocate video buffer memory for the MMAP type */
        if (memory == V4L2_MEMORY_MMAP) {
            ret = __vb2_buf_mem_alloc(vb);
            if (ret) {
                dprintk(1, "Failed allocating memory for "
                        "buffer %d\n", buffer);
                kfree(vb);
                break;
            }
            /*
             * Call the driver-provided buffer initialization
             * callback, if given. An error in initialization
             * results in queue setup failure.
             */
            ret = call_qop(q, buf_init, vb);
            if (ret) {
                dprintk(1, "Buffer %d %p initialization"
                    " failed\n", buffer, vb);
                __vb2_buf_mem_free(vb);
                kfree(vb);
                break;
            }
        }

        q->bufs[q->num_buffers + buffer] = vb;
    }

    __setup_offsets(q, buffer);

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

    return buffer;
}

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 == V4L2_MEMORY_MMAP)
            __vb2_buf_mem_free(vb);
        else
            __vb2_buf_userptr_put(vb);
    }
}

static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
{
    unsigned int buffer;

    /* Call driver-provided cleanup function for each buffer, if provided */
    if (q->ops->buf_cleanup) {
        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
            if (NULL == q->bufs[buffer])
                continue;
            q->ops->buf_cleanup(q->bufs[buffer]);
        }
    }

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

    /* 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);
}

static int __verify_planes_array(struct vb2_buffer *vb, const struct v4l2_buffer *b)
{
    if (!V4L2_TYPE_IS_MULTIPLANAR(b->type))
        return 0;

    /* Is memory for copying plane information present? */
    if (NULL == b->m.planes) {
        dprintk(1, "Multi-planar buffer passed but "
               "planes array not provided\n");
        return -EINVAL;
    }

    if (b->length < vb->num_planes || b->length > VIDEO_MAX_PLANES) {
        dprintk(1, "Incorrect planes array length, "
               "expected %d, got %d\n", vb->num_planes, b->length);
        return -EINVAL;
    }

    return 0;
}

static bool __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(q, num_users, mem_priv) > 1)
            return true;
    }
    return false;
}

static bool __buffers_in_use(struct vb2_queue *q)
{
    unsigned int buffer;
    for (buffer = 0; buffer < q->num_buffers; ++buffer) {
        if (__buffer_in_use(q, q->bufs[buffer]))
            return true;
    }
    return false;
}

static void __fill_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b)
{
    struct vb2_queue *q = vb->vb2_queue;

    /* Copy back data such as timestamp, flags, etc. */
    memcpy(b, &vb->v4l2_buf, offsetof(struct v4l2_buffer, m));
    b->reserved2 = vb->v4l2_buf.reserved2;
    b->reserved = vb->v4l2_buf.reserved;

    if (V4L2_TYPE_IS_MULTIPLANAR(q->type)) {
        /*
         * Fill in plane-related data if userspace provided an array
         * for it. The caller has already verified memory and size.
         */
        b->length = vb->num_planes;
        memcpy(b->m.planes, vb->v4l2_planes,
            b->length * sizeof(struct v4l2_plane));
    } else {
        /*
         * We use length and offset in v4l2_planes array even for
         * single-planar buffers, but userspace does not.
         */
        b->length = vb->v4l2_planes[0].length;
        b->bytesused = vb->v4l2_planes[0].bytesused;
        if (q->memory == V4L2_MEMORY_MMAP)
            b->m.offset = vb->v4l2_planes[0].m.mem_offset;
        else if (q->memory == V4L2_MEMORY_USERPTR)
            b->m.userptr = vb->v4l2_planes[0].m.userptr;
    }

    /*
     * Clear any buffer state related flags.
     */
    b->flags &= ~V4L2_BUFFER_STATE_FLAGS;

    switch (vb->state) {
    case VB2_BUF_STATE_QUEUED:
    case VB2_BUF_STATE_ACTIVE:
        b->flags |= V4L2_BUF_FLAG_QUEUED;
        break;
    case VB2_BUF_STATE_ERROR:
        b->flags |= V4L2_BUF_FLAG_ERROR;
        /* fall through */
    case VB2_BUF_STATE_DONE:
        b->flags |= V4L2_BUF_FLAG_DONE;
        break;
    case VB2_BUF_STATE_PREPARED:
        b->flags |= V4L2_BUF_FLAG_PREPARED;
        break;
    case VB2_BUF_STATE_DEQUEUED:
        /* nothing */
        break;
    }

    if (__buffer_in_use(q, vb))
        b->flags |= V4L2_BUF_FLAG_MAPPED;
}

int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
{
    struct vb2_buffer *vb;
    int ret;

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

    if (b->index >= q->num_buffers) {
        dprintk(1, "querybuf: buffer index out of range\n");
        return -EINVAL;
    }
    vb = q->bufs[b->index];
    ret = __verify_planes_array(vb, b);
    if (!ret)
        __fill_v4l2_buffer(vb, b);
    return ret;
}
EXPORT_SYMBOL(vb2_querybuf);

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;
}

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;
}

static int __verify_memory_type(struct vb2_queue *q,
        enum v4l2_memory memory, enum v4l2_buf_type type)
{
    if (memory != V4L2_MEMORY_MMAP && memory != V4L2_MEMORY_USERPTR) {
        dprintk(1, "reqbufs: unsupported memory type\n");
        return -EINVAL;
    }

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

    /*
     * Make sure all the required memory ops for given memory type
     * are available.
     */
    if (memory == V4L2_MEMORY_MMAP && __verify_mmap_ops(q)) {
        dprintk(1, "reqbufs: MMAP for current setup unsupported\n");
        return -EINVAL;
    }

    if (memory == V4L2_MEMORY_USERPTR && __verify_userptr_ops(q)) {
        dprintk(1, "reqbufs: USERPTR 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 (q->fileio) {
        dprintk(1, "reqbufs: file io in progress\n");
        return -EBUSY;
    }
    return 0;
}

static int __reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
{
    unsigned int num_buffers, allocated_buffers, num_planes = 0;
    int ret;

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

    if (req->count == 0 || q->num_buffers != 0 || q->memory != req->memory) {
        /*
         * We already have buffers allocated, so first check if they
         * are not in use and can be freed.
         */
        if (q->memory == V4L2_MEMORY_MMAP && __buffers_in_use(q)) {
            dprintk(1, "reqbufs: memory in use, cannot free\n");
            return -EBUSY;
        }

        __vb2_queue_free(q, q->num_buffers);

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

    /*
     * Make sure the requested values and current defaults are sane.
     */
    num_buffers = min_t(unsigned int, req->count, VIDEO_MAX_FRAME);
    memset(q->plane_sizes, 0, sizeof(q->plane_sizes));
    memset(q->alloc_ctx, 0, sizeof(q->alloc_ctx));
    q->memory = req->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, NULL, &num_buffers, &num_planes,
               q->plane_sizes, q->alloc_ctx);
    if (ret)
        return ret;

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

    allocated_buffers = ret;

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

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

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

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

    q->num_buffers = allocated_buffers;

    if (ret < 0) {
        __vb2_queue_free(q, allocated_buffers);
        return ret;
    }

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

    return 0;
}

int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
{
    int ret = __verify_memory_type(q, req->memory, req->type);

    return ret ? ret : __reqbufs(q, req);
}
EXPORT_SYMBOL_GPL(vb2_reqbufs);

static int __create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
{
    unsigned int num_planes = 0, num_buffers, allocated_buffers;
    int ret;

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

    if (!q->num_buffers) {
        memset(q->plane_sizes, 0, sizeof(q->plane_sizes));
        memset(q->alloc_ctx, 0, sizeof(q->alloc_ctx));
        q->memory = create->memory;
    }

    num_buffers = min(create->count, VIDEO_MAX_FRAME - q->num_buffers);

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

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

    allocated_buffers = ret;

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

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

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

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

    q->num_buffers += allocated_buffers;

    if (ret < 0) {
        __vb2_queue_free(q, allocated_buffers);
        return -ENOMEM;
    }

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

    return 0;
}

int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
{
    int ret = __verify_memory_type(q, create->memory, create->format.type);

    create->index = q->num_buffers;
    if (create->count == 0)
        return ret != -EBUSY ? ret : 0;
    return ret ? ret : __create_bufs(q, create);
}
EXPORT_SYMBOL_GPL(vb2_create_bufs);

void *vb2_plane_vaddr(struct vb2_buffer *vb, unsigned int plane_no)
{
    struct vb2_queue *q = vb->vb2_queue;

    if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
        return NULL;

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

}
EXPORT_SYMBOL_GPL(vb2_plane_vaddr);

void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
{
    struct vb2_queue *q = vb->vb2_queue;

    if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
        return NULL;

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

void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
{
    struct vb2_queue *q = vb->vb2_queue;
    unsigned long flags;

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

    if (state != VB2_BUF_STATE_DONE && state != VB2_BUF_STATE_ERROR)
        return;

    dprintk(4, "Done processing on buffer %d, state: %d\n",
            vb->v4l2_buf.index, vb->state);

    /* Add the buffer to the done buffers list */
    spin_lock_irqsave(&q->done_lock, flags);
    vb->state = state;
    list_add_tail(&vb->done_entry, &q->done_list);
    atomic_dec(&q->queued_count);
    spin_unlock_irqrestore(&q->done_lock, flags);

    /* Inform any processes that may be waiting for buffers */
    wake_up(&q->done_wq);
}
EXPORT_SYMBOL_GPL(vb2_buffer_done);

static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b,
                struct v4l2_plane *v4l2_planes)
{
    unsigned int plane;

    if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
        /* Fill in driver-provided information for OUTPUT types */
        if (V4L2_TYPE_IS_OUTPUT(b->type)) {
            /*
             * Will have to go up to b->length when API starts
             * accepting variable number of planes.
             */
            for (plane = 0; plane < vb->num_planes; ++plane) {
                v4l2_planes[plane].bytesused =
                    b->m.planes[plane].bytesused;
                v4l2_planes[plane].data_offset =
                    b->m.planes[plane].data_offset;
            }
        }

        if (b->memory == V4L2_MEMORY_USERPTR) {
            for (plane = 0; plane < vb->num_planes; ++plane) {
                v4l2_planes[plane].m.userptr =
                    b->m.planes[plane].m.userptr;
                v4l2_planes[plane].length =
                    b->m.planes[plane].length;
            }
        }
    } else {
        /*
         * Single-planar buffers do not use planes array,
         * so fill in relevant v4l2_buffer struct fields instead.
         * In videobuf we use our internal V4l2_planes struct for
         * single-planar buffers as well, for simplicity.
         */
        if (V4L2_TYPE_IS_OUTPUT(b->type))
            v4l2_planes[0].bytesused = b->bytesused;

        if (b->memory == V4L2_MEMORY_USERPTR) {
            v4l2_planes[0].m.userptr = b->m.userptr;
            v4l2_planes[0].length = b->length;
        }
    }

    vb->v4l2_buf.field = b->field;
    vb->v4l2_buf.timestamp = b->timestamp;
    vb->v4l2_buf.flags = b->flags & ~V4L2_BUFFER_STATE_FLAGS;
}

static int __qbuf_userptr(struct vb2_buffer *vb, const struct v4l2_buffer *b)
{
    struct v4l2_plane planes[VIDEO_MAX_PLANES];
    struct vb2_queue *q = vb->vb2_queue;
    void *mem_priv;
    unsigned int plane;
    int ret;
    int write = !V4L2_TYPE_IS_OUTPUT(q->type);

    /* Copy relevant information provided by the userspace */
    __fill_vb2_buffer(vb, b, planes);

    for (plane = 0; plane < vb->num_planes; ++plane) {
        /* Skip the plane if already verified */
        if (vb->v4l2_planes[plane].m.userptr &&
            vb->v4l2_planes[plane].m.userptr == planes[plane].m.userptr
            && vb->v4l2_planes[plane].length == planes[plane].length)
            continue;

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

        /* Check if the provided plane buffer is large enough */
        if (planes[plane].length < q->plane_sizes[plane]) {
            ret = -EINVAL;
            goto err;
        }

        /* Release previously acquired memory if present */
        if (vb->planes[plane].mem_priv)
            call_memop(q, put_userptr, vb->planes[plane].mem_priv);

        vb->planes[plane].mem_priv = NULL;
        vb->v4l2_planes[plane].m.userptr = 0;
        vb->v4l2_planes[plane].length = 0;

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

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

    /*
     * Now that everything is in order, copy relevant information
     * provided by userspace.
     */
    for (plane = 0; plane < vb->num_planes; ++plane)
        vb->v4l2_planes[plane] = planes[plane];

    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_memop(q, put_userptr, vb->planes[plane].mem_priv);
        vb->planes[plane].mem_priv = NULL;
        vb->v4l2_planes[plane].m.userptr = 0;
        vb->v4l2_planes[plane].length = 0;
    }

    return ret;
}

static int __qbuf_mmap(struct vb2_buffer *vb, const struct v4l2_buffer *b)
{
    __fill_vb2_buffer(vb, b, vb->v4l2_planes);
    return 0;
}

static void __enqueue_in_driver(struct vb2_buffer *vb)
{
    struct vb2_queue *q = vb->vb2_queue;

    vb->state = VB2_BUF_STATE_ACTIVE;
    atomic_inc(&q->queued_count);
    q->ops->buf_queue(vb);
}

static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
{
    struct vb2_queue *q = vb->vb2_queue;
    int ret;

    switch (q->memory) {
    case V4L2_MEMORY_MMAP:
        ret = __qbuf_mmap(vb, b);
        break;
    case V4L2_MEMORY_USERPTR:
        ret = __qbuf_userptr(vb, b);
        break;
    default:
        WARN(1, "Invalid queue type\n");
        ret = -EINVAL;
    }

    if (!ret)
        ret = call_qop(q, buf_prepare, vb);
    if (ret)
        dprintk(1, "qbuf: buffer preparation failed: %d\n", ret);
    else
        vb->state = VB2_BUF_STATE_PREPARED;

    return ret;
}

int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b)
{
    struct vb2_buffer *vb;
    int ret;

    if (q->fileio) {
        dprintk(1, "%s(): file io in progress\n", __func__);
        return -EBUSY;
    }

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

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

    vb = q->bufs[b->index];
    if (NULL == vb) {
        /* Should never happen */
        dprintk(1, "%s(): buffer is NULL\n", __func__);
        return -EINVAL;
    }

    if (b->memory != q->memory) {
        dprintk(1, "%s(): invalid memory type\n", __func__);
        return -EINVAL;
    }

    if (vb->state != VB2_BUF_STATE_DEQUEUED) {
        dprintk(1, "%s(): invalid buffer state %d\n", __func__, vb->state);
        return -EINVAL;
    }
    ret = __verify_planes_array(vb, b);
    if (ret < 0)
        return ret;
    ret = __buf_prepare(vb, b);
    if (ret < 0)
        return ret;

    __fill_v4l2_buffer(vb, b);

    return 0;
}
EXPORT_SYMBOL_GPL(vb2_prepare_buf);

int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
{
    struct rw_semaphore *mmap_sem = NULL;
    struct vb2_buffer *vb;
    int ret = 0;

    /*
     * In case of user pointer buffers vb2 allocator needs to get direct
     * access to userspace pages. This requires getting read access on
     * mmap semaphore in the current process structure. The same
     * semaphore is taken before calling mmap operation, while both mmap
     * and qbuf are called by the driver or v4l2 core with driver's lock
     * held. To avoid a AB-BA deadlock (mmap_sem then driver's lock in
     * mmap and driver's lock then mmap_sem in qbuf) the videobuf2 core
     * release driver's lock, takes mmap_sem and then takes again driver's
     * lock.
     *
     * To avoid race with other vb2 calls, which might be called after
     * releasing driver's lock, this operation is performed at the
     * beggining of qbuf processing. This way the queue status is
     * consistent after getting driver's lock back.
     */
    if (q->memory == V4L2_MEMORY_USERPTR) {
        mmap_sem = &current->mm->mmap_sem;
        call_qop(q, wait_prepare, q);
        down_read(mmap_sem);
        call_qop(q, wait_finish, q);
    }

    if (q->fileio) {
        dprintk(1, "qbuf: file io in progress\n");
        ret = -EBUSY;
        goto unlock;
    }

    if (b->type != q->type) {
        dprintk(1, "qbuf: invalid buffer type\n");
        ret = -EINVAL;
        goto unlock;
    }

    if (b->index >= q->num_buffers) {
        dprintk(1, "qbuf: buffer index out of range\n");
        ret = -EINVAL;
        goto unlock;
    }

    vb = q->bufs[b->index];
    if (NULL == vb) {
        /* Should never happen */
        dprintk(1, "qbuf: buffer is NULL\n");
        ret = -EINVAL;
        goto unlock;
    }

    if (b->memory != q->memory) {
        dprintk(1, "qbuf: invalid memory type\n");
        ret = -EINVAL;
        goto unlock;
    }
    ret = __verify_planes_array(vb, b);
    if (ret)
        goto unlock;

    switch (vb->state) {
    case VB2_BUF_STATE_DEQUEUED:
        ret = __buf_prepare(vb, b);
        if (ret)
            goto unlock;
    case VB2_BUF_STATE_PREPARED:
        break;
    default:
        dprintk(1, "qbuf: buffer already in use\n");
        ret = -EINVAL;
        goto unlock;
    }

    /*
     * 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);
    vb->state = VB2_BUF_STATE_QUEUED;

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

    /* Fill buffer information for the userspace */
    __fill_v4l2_buffer(vb, b);

    dprintk(1, "qbuf of buffer %d succeeded\n", vb->v4l2_buf.index);
unlock:
    if (mmap_sem)
        up_read(mmap_sem);
    return ret;
}
EXPORT_SYMBOL_GPL(vb2_qbuf);

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 (!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_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);

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

static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
                struct v4l2_buffer *b, int nonblocking)
{
    unsigned long flags;
    int ret;

    /*
     * 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 v4l2_buffer can handle all
     * the planes.
     */
    ret = __verify_planes_array(*vb, b);
    if (!ret)
        list_del(&(*vb)->done_entry);
    spin_unlock_irqrestore(&q->done_lock, flags);

    return ret;
}

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;
    }

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

int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
{
    struct vb2_buffer *vb = NULL;
    int ret;

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

    if (b->type != q->type) {
        dprintk(1, "dqbuf: invalid buffer type\n");
        return -EINVAL;
    }
    ret = __vb2_get_done_vb(q, &vb, b, nonblocking);
    if (ret < 0)
        return ret;

    ret = call_qop(q, buf_finish, vb);
    if (ret) {
        dprintk(1, "dqbuf: buffer finish failed\n");
        return ret;
    }

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

    /* Fill buffer information for the userspace */
    __fill_v4l2_buffer(vb, b);
    /* Remove from videobuf queue */
    list_del(&vb->queued_entry);

    dprintk(1, "dqbuf of buffer %d, with state %d\n",
            vb->v4l2_buf.index, vb->state);

    vb->state = VB2_BUF_STATE_DEQUEUED;
    return 0;
}
EXPORT_SYMBOL_GPL(vb2_dqbuf);

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->streaming)
        call_qop(q, stop_streaming, q);
    q->streaming = 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->queued_count, 0);
    wake_up_all(&q->done_wq);

    /*
     * Reinitialize all buffers for next use.
     */
    for (i = 0; i < q->num_buffers; ++i)
        q->bufs[i]->state = VB2_BUF_STATE_DEQUEUED;
}

int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
{
    struct vb2_buffer *vb;
    int ret;

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

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

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

    /*
     * 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);

    /*
     * Let driver notice that streaming state has been enabled.
     */
    ret = call_qop(q, start_streaming, q, atomic_read(&q->queued_count));
    if (ret) {
        dprintk(1, "streamon: driver refused to start streaming\n");
        __vb2_queue_cancel(q);
        return ret;
    }

    q->streaming = 1;

    dprintk(3, "Streamon successful\n");
    return 0;
}
EXPORT_SYMBOL_GPL(vb2_streamon);


int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
{
    if (q->fileio) {
        dprintk(1, "streamoff: file io in progress\n");
        return -EBUSY;
    }

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

    if (!q->streaming) {
        dprintk(1, "streamoff: not streaming\n");
        return -EINVAL;
    }

    /*
     * Cancel will pause streaming and remove all buffers from the driver
     * and videobuf, effectively returning control over them to userspace.
     */
    __vb2_queue_cancel(q);

    dprintk(3, "Streamoff successful\n");
    return 0;
}
EXPORT_SYMBOL_GPL(vb2_streamoff);

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->v4l2_planes[plane].m.mem_offset == off) {
                *_buffer = buffer;
                *_plane = plane;
                return 0;
            }
        }
    }

    return -EINVAL;
}

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, plane;
    int ret;

    if (q->memory != V4L2_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 (V4L2_TYPE_IS_OUTPUT(q->type)) {
        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;
        }
    }

    /*
     * 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];

    ret = call_memop(q, mmap, vb->planes[plane].mem_priv, vma);
    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;
    int ret;

    if (q->memory != V4L2_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];

    return (unsigned long)vb2_plane_vaddr(vb, plane);
}
EXPORT_SYMBOL_GPL(vb2_get_unmapped_area);
#endif

static int __vb2_init_fileio(struct vb2_queue *q, int read);
static int __vb2_cleanup_fileio(struct vb2_queue *q);

unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait)
{
    struct video_device *vfd = video_devdata(file);
    unsigned long req_events = poll_requested_events(wait);
    struct vb2_buffer *vb = NULL;
    unsigned int res = 0;
    unsigned long flags;

    if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)) {
        struct v4l2_fh *fh = file->private_data;

        if (v4l2_event_pending(fh))
            res = POLLPRI;
        else if (req_events & POLLPRI)
            poll_wait(file, &fh->wait, wait);
    }

    /*
     * Start file I/O emulator only if streaming API has not been used yet.
     */
    if (q->num_buffers == 0 && q->fileio == NULL) {
        if (!V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_READ) &&
                (req_events & (POLLIN | POLLRDNORM))) {
            if (__vb2_init_fileio(q, 1))
                return res | POLLERR;
        }
        if (V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_WRITE) &&
                (req_events & (POLLOUT | POLLWRNORM))) {
            if (__vb2_init_fileio(q, 0))
                return res | POLLERR;
            /*
             * Write to OUTPUT queue can be done immediately.
             */
            return res | POLLOUT | POLLWRNORM;
        }
    }

    /*
     * There is nothing to wait for if no buffers have already been queued.
     */
    if (list_empty(&q->queued_list))
        return res | POLLERR;

    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 (V4L2_TYPE_IS_OUTPUT(q->type)) ?
                res | POLLOUT | POLLWRNORM :
                res | POLLIN | POLLRDNORM;
    }
    return res;
}
EXPORT_SYMBOL_GPL(vb2_poll);

int vb2_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);
    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_queue_init);

void vb2_queue_release(struct vb2_queue *q)
{
    __vb2_cleanup_fileio(q);
    __vb2_queue_cancel(q);
    __vb2_queue_free(q, q->num_buffers);
}
EXPORT_SYMBOL_GPL(vb2_queue_release);

struct vb2_fileio_buf {
    void *vaddr;
    unsigned int size;
    unsigned int pos;
    unsigned int queued:1;
};

struct vb2_fileio_data {
    struct v4l2_requestbuffers req;
    struct v4l2_buffer b;
    struct vb2_fileio_buf bufs[VIDEO_MAX_FRAME];
    unsigned int index;
    unsigned int q_count;
    unsigned int dq_count;
    unsigned int flags;
};

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 ((read && !(q->io_modes & VB2_READ)) ||
       (!read && !(q->io_modes & VB2_WRITE)))
        BUG();

    /*
     * 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, flags %08x\n",
        (read) ? "read" : "write", count, q->io_flags);

    fileio = kzalloc(sizeof(struct vb2_fileio_data), GFP_KERNEL);
    if (fileio == NULL)
        return -ENOMEM;

    fileio->flags = q->io_flags;

    /*
     * Request buffers and use MMAP type to force driver
     * to allocate buffers by itself.
     */
    fileio->req.count = count;
    fileio->req.memory = V4L2_MEMORY_MMAP;
    fileio->req.type = q->type;
    ret = vb2_reqbufs(q, &fileio->req);
    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)
            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++) {
            struct v4l2_buffer *b = &fileio->b;
            memset(b, 0, sizeof(*b));
            b->type = q->type;
            b->memory = q->memory;
            b->index = i;
            ret = vb2_qbuf(q, b);
            if (ret)
                goto err_reqbufs;
            fileio->bufs[i].queued = 1;
        }

        /*
         * Start streaming.
         */
        ret = vb2_streamon(q, q->type);
        if (ret)
            goto err_reqbufs;
    }

    q->fileio = fileio;

    return ret;

err_reqbufs:
    fileio->req.count = 0;
    vb2_reqbufs(q, &fileio->req);

err_kfree:
    kfree(fileio);
    return ret;
}

static int __vb2_cleanup_fileio(struct vb2_queue *q)
{
    struct vb2_fileio_data *fileio = q->fileio;

    if (fileio) {
        /*
         * Hack fileio context to enable direct calls to vb2 ioctl
         * interface.
         */
        q->fileio = NULL;

        vb2_streamoff(q, q->type);
        fileio->req.count = 0;
        vb2_reqbufs(q, &fileio->req);
        kfree(fileio);
        dprintk(3, "file io emulator closed\n");
    }
    return 0;
}

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;
    int ret, index;

    dprintk(3, "file io: 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 (!q->fileio) {
        ret = __vb2_init_fileio(q, read);
        dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
        if (ret)
            return ret;
    }
    fileio = q->fileio;

    /*
     * Hack fileio context to enable direct calls to vb2 ioctl interface.
     * The pointer will be restored before returning from this function.
     */
    q->fileio = NULL;

    index = fileio->index;
    buf = &fileio->bufs[index];

    /*
     * Check if we need to dequeue the buffer.
     */
    if (buf->queued) {
        struct vb2_buffer *vb;

        /*
         * Call vb2_dqbuf to get buffer back.
         */
        memset(&fileio->b, 0, sizeof(fileio->b));
        fileio->b.type = q->type;
        fileio->b.memory = q->memory;
        fileio->b.index = index;
        ret = vb2_dqbuf(q, &fileio->b, nonblock);
        dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
        if (ret)
            goto end;
        fileio->dq_count += 1;

        /*
         * Get number of bytes filled by the driver
         */
        vb = q->bufs[index];
        buf->size = vb2_get_plane_payload(vb, 0);
        buf->queued = 0;
    }

    /*
     * 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, "file io: 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, "file io: error copying data\n");
        ret = -EFAULT;
        goto end;
    }

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

    /*
     * Queue next buffer if required.
     */
    if (buf->pos == buf->size ||
       (!read && (fileio->flags & VB2_FILEIO_WRITE_IMMEDIATELY))) {
        /*
         * Check if this is the last buffer to read.
         */
        if (read && (fileio->flags & VB2_FILEIO_READ_ONCE) &&
            fileio->dq_count == 1) {
            dprintk(3, "file io: read limit reached\n");
            /*
             * Restore fileio pointer and release the context.
             */
            q->fileio = fileio;
            return __vb2_cleanup_fileio(q);
        }

        /*
         * Call vb2_qbuf and give buffer to the driver.
         */
        memset(&fileio->b, 0, sizeof(fileio->b));
        fileio->b.type = q->type;
        fileio->b.memory = q->memory;
        fileio->b.index = index;
        fileio->b.bytesused = buf->pos;
        ret = vb2_qbuf(q, &fileio->b);
        dprintk(5, "file io: vb2_dbuf result: %d\n", ret);
        if (ret)
            goto end;

        /*
         * Buffer has been queued, update the status
         */
        buf->pos = 0;
        buf->queued = 1;
        buf->size = q->bufs[0]->v4l2_planes[0].length;
        fileio->q_count += 1;

        /*
         * Switch to the next buffer
         */
        fileio->index = (index + 1) % q->num_buffers;

        /*
         * Start streaming if required.
         */
        if (!read && !q->streaming) {
            ret = vb2_streamon(q, q->type);
            if (ret)
                goto end;
        }
    }

    /*
     * Return proper number of bytes processed.
     */
    if (ret == 0)
        ret = count;
end:
    /*
     * Restore the fileio context and block vb2 ioctl interface.
     */
    q->fileio = fileio;
    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, char __user *data, size_t count,
        loff_t *ppos, int nonblocking)
{
    return __vb2_perform_fileio(q, data, count, ppos, nonblocking, 0);
}
EXPORT_SYMBOL_GPL(vb2_write);


/*
 * The following functions are not part of the vb2 core API, but are helper
 * functions that plug into struct v4l2_ioctl_ops, struct v4l2_file_operations
 * and struct vb2_ops.
 * They contain boilerplate code that most if not all drivers have to do
 * and so they simplify the driver code.
 */

/* The queue is busy if there is a owner and you are not that owner. */
static inline bool vb2_queue_is_busy(struct video_device *vdev, struct file *file)
{
    return vdev->queue->owner && vdev->queue->owner != file->private_data;
}

/* vb2 ioctl helpers */

int vb2_ioctl_reqbufs(struct file *file, void *priv,
              struct v4l2_requestbuffers *p)
{
    struct video_device *vdev = video_devdata(file);
    int res = __verify_memory_type(vdev->queue, p->memory, p->type);

    if (res)
        return res;
    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    res = __reqbufs(vdev->queue, p);
    /* If count == 0, then the owner has released all buffers and he
       is no longer owner of the queue. Otherwise we have a new owner. */
    if (res == 0)
        vdev->queue->owner = p->count ? file->private_data : NULL;
    return res;
}
EXPORT_SYMBOL_GPL(vb2_ioctl_reqbufs);

int vb2_ioctl_create_bufs(struct file *file, void *priv,
              struct v4l2_create_buffers *p)
{
    struct video_device *vdev = video_devdata(file);
    int res = __verify_memory_type(vdev->queue, p->memory, p->format.type);

    p->index = vdev->queue->num_buffers;
    /* If count == 0, then just check if memory and type are valid.
       Any -EBUSY result from __verify_memory_type can be mapped to 0. */
    if (p->count == 0)
        return res != -EBUSY ? res : 0;
    if (res)
        return res;
    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    res = __create_bufs(vdev->queue, p);
    if (res == 0)
        vdev->queue->owner = file->private_data;
    return res;
}
EXPORT_SYMBOL_GPL(vb2_ioctl_create_bufs);

int vb2_ioctl_prepare_buf(struct file *file, void *priv,
              struct v4l2_buffer *p)
{
    struct video_device *vdev = video_devdata(file);

    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    return vb2_prepare_buf(vdev->queue, p);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_prepare_buf);

int vb2_ioctl_querybuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    struct video_device *vdev = video_devdata(file);

    /* No need to call vb2_queue_is_busy(), anyone can query buffers. */
    return vb2_querybuf(vdev->queue, p);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_querybuf);

int vb2_ioctl_qbuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    struct video_device *vdev = video_devdata(file);

    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    return vb2_qbuf(vdev->queue, p);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_qbuf);

int vb2_ioctl_dqbuf(struct file *file, void *priv, struct v4l2_buffer *p)
{
    struct video_device *vdev = video_devdata(file);

    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    return vb2_dqbuf(vdev->queue, p, file->f_flags & O_NONBLOCK);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_dqbuf);

int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i)
{
    struct video_device *vdev = video_devdata(file);

    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    return vb2_streamon(vdev->queue, i);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_streamon);

int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i)
{
    struct video_device *vdev = video_devdata(file);

    if (vb2_queue_is_busy(vdev, file))
        return -EBUSY;
    return vb2_streamoff(vdev->queue, i);
}
EXPORT_SYMBOL_GPL(vb2_ioctl_streamoff);

/* v4l2_file_operations helpers */

int vb2_fop_mmap(struct file *file, struct vm_area_struct *vma)
{
    struct video_device *vdev = video_devdata(file);

    return vb2_mmap(vdev->queue, vma);
}
EXPORT_SYMBOL_GPL(vb2_fop_mmap);

int vb2_fop_release(struct file *file)
{
    struct video_device *vdev = video_devdata(file);

    if (file->private_data == vdev->queue->owner) {
        vb2_queue_release(vdev->queue);
        vdev->queue->owner = NULL;
    }
    return v4l2_fh_release(file);
}
EXPORT_SYMBOL_GPL(vb2_fop_release);

ssize_t vb2_fop_write(struct file *file, char __user *buf,
        size_t count, loff_t *ppos)
{
    struct video_device *vdev = video_devdata(file);
    struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
    int err = -EBUSY;

    if (lock && mutex_lock_interruptible(lock))
        return -ERESTARTSYS;
    if (vb2_queue_is_busy(vdev, file))
        goto exit;
    err = vb2_write(vdev->queue, buf, count, ppos,
               file->f_flags & O_NONBLOCK);
    if (vdev->queue->fileio)
        vdev->queue->owner = file->private_data;
exit:
    if (lock)
        mutex_unlock(lock);
    return err;
}
EXPORT_SYMBOL_GPL(vb2_fop_write);

ssize_t vb2_fop_read(struct file *file, char __user *buf,
        size_t count, loff_t *ppos)
{
    struct video_device *vdev = video_devdata(file);
    struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
    int err = -EBUSY;

    if (lock && mutex_lock_interruptible(lock))
        return -ERESTARTSYS;
    if (vb2_queue_is_busy(vdev, file))
        goto exit;
    err = vb2_read(vdev->queue, buf, count, ppos,
               file->f_flags & O_NONBLOCK);
    if (vdev->queue->fileio)
        vdev->queue->owner = file->private_data;
exit:
    if (lock)
        mutex_unlock(lock);
    return err;
}
EXPORT_SYMBOL_GPL(vb2_fop_read);

unsigned int vb2_fop_poll(struct file *file, poll_table *wait)
{
    struct video_device *vdev = video_devdata(file);
    struct vb2_queue *q = vdev->queue;
    struct mutex *lock = q->lock ? q->lock : vdev->lock;
    unsigned long req_events = poll_requested_events(wait);
    unsigned res;
    void *fileio;
    bool must_lock = false;

    /* Try to be smart: only lock if polling might start fileio,
       otherwise locking will only introduce unwanted delays. */
    if (q->num_buffers == 0 && q->fileio == NULL) {
        if (!V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_READ) &&
                (req_events & (POLLIN | POLLRDNORM)))
            must_lock = true;
        else if (V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_WRITE) &&
                (req_events & (POLLOUT | POLLWRNORM)))
            must_lock = true;
    }

    /* If locking is needed, but this helper doesn't know how, then you
       shouldn't be using this helper but you should write your own. */
    WARN_ON(must_lock && !lock);

    if (must_lock && lock && mutex_lock_interruptible(lock))
        return POLLERR;

    fileio = q->fileio;

    res = vb2_poll(vdev->queue, file, wait);

    /* If fileio was started, then we have a new queue owner. */
    if (must_lock && !fileio && q->fileio)
        q->owner = file->private_data;
    if (must_lock && lock)
        mutex_unlock(lock);
    return res;
}
EXPORT_SYMBOL_GPL(vb2_fop_poll);

#ifndef CONFIG_MMU
unsigned long vb2_fop_get_unmapped_area(struct file *file, unsigned long addr,
        unsigned long len, unsigned long pgoff, unsigned long flags)
{
    struct video_device *vdev = video_devdata(file);

    return vb2_get_unmapped_area(vdev->queue, addr, len, pgoff, flags);
}
EXPORT_SYMBOL_GPL(vb2_fop_get_unmapped_area);
#endif

/* vb2_ops helpers. Only use if vq->lock is non-NULL. */

void vb2_ops_wait_prepare(struct vb2_queue *vq)
{
    mutex_unlock(vq->lock);
}
EXPORT_SYMBOL_GPL(vb2_ops_wait_prepare);

void vb2_ops_wait_finish(struct vb2_queue *vq)
{
    mutex_lock(vq->lock);
}
EXPORT_SYMBOL_GPL(vb2_ops_wait_finish);

MODULE_DESCRIPTION("Driver helper framework for Video for Linux 2");
MODULE_AUTHOR("Pawel Osciak <[email protected]>, Marek Szyprowski");
MODULE_LICENSE("GPL");