1 files changed, 1820 insertions, 0 deletions

diff --git a/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c
new file mode 100644
index 00000000000..3015e600094
--- /dev/null
+++ b/drivers/media/video/videobuf2-core.c
@@ -0,0 +1,1820 @@
+/*
+ * videobuf2-core.c - V4L2 driver helper framework
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ *
+ * Author: Pawel Osciak <pawel@osciak.com>
+ *         Marek Szyprowski <m.szyprowski@samsung.com>
+ *
+ * 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/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, plane, 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)
+
+/**
+ * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
+ */
+static int __vb2_buf_mem_alloc(struct vb2_buffer *vb,
+                                unsigned long *plane_sizes)
+{
+        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, plane, alloc, q->alloc_ctx[plane],
+                                        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 = plane_sizes[plane];
+        }
+
+        return 0;
+free:
+        /* Free already allocated memory if one of the allocations failed */
+        for (; plane > 0; --plane)
+                call_memop(q, plane, put, vb->planes[plane - 1].mem_priv);
+
+        return -ENOMEM;
+}
+
+/**
+ * __vb2_buf_mem_free() - free memory of the given buffer
+ */
+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, plane, 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);
+        }
+}
+
+/**
+ * __vb2_buf_userptr_put() - release userspace memory associated with
+ * a USERPTR buffer
+ */
+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) {
+                void *mem_priv = vb->planes[plane].mem_priv;
+
+                if (mem_priv) {
+                        call_memop(q, plane, put_userptr, mem_priv);
+                        vb->planes[plane].mem_priv = NULL;
+                }
+        }
+}
+
+/**
+ * __setup_offsets() - setup unique offsets ("cookies") for every plane in
+ * every buffer on the queue
+ */
+static void __setup_offsets(struct vb2_queue *q)
+{
+        unsigned int buffer, plane;
+        struct vb2_buffer *vb;
+        unsigned long off = 0;
+
+        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
+                vb = q->bufs[buffer];
+                if (!vb)
+                        continue;
+
+                for (plane = 0; plane < vb->num_planes; ++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);
+                }
+        }
+}
+
+/**
+ * __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 v4l2_memory memory,
+                             unsigned int num_buffers, unsigned int num_planes,
+                             unsigned long plane_sizes[])
+{
+        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 = 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, plane_sizes);
+                        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[buffer] = vb;
+        }
+
+        q->num_buffers = buffer;
+
+        __setup_offsets(q);
+
+        dprintk(1, "Allocated %d buffers, %d plane(s) each\n",
+                        q->num_buffers, 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 buffer;
+        struct vb2_buffer *vb;
+
+        for (buffer = 0; 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);
+        }
+}
+
+/**
+ * __vb2_queue_free() - free the queue - video memory and related information
+ * and return the queue to an uninitialized state. Might be called even if the
+ * queue has already been freed.
+ */
+static void __vb2_queue_free(struct vb2_queue *q)
+{
+        unsigned int buffer;
+
+        /* Call driver-provided cleanup function for each buffer, if provided */
+        if (q->ops->buf_cleanup) {
+                for (buffer = 0; 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);
+
+        /* Free videobuf buffers */
+        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
+                kfree(q->bufs[buffer]);
+                q->bufs[buffer] = NULL;
+        }
+
+        q->num_buffers = 0;
+        q->memory = 0;
+}
+
+/**
+ * __verify_planes_array() - verify that the planes array passed in struct
+ * v4l2_buffer from userspace can be safely used
+ */
+static int __verify_planes_array(struct vb2_buffer *vb, struct v4l2_buffer *b)
+{
+        /* 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;
+}
+
+/**
+ * __fill_v4l2_buffer() - fill in a struct v4l2_buffer with information to be
+ * returned to userspace
+ */
+static int __fill_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b)
+{
+        struct vb2_queue *q = vb->vb2_queue;
+        int ret = 0;
+
+        /* Copy back data such as timestamp, flags, input, etc. */
+        memcpy(b, &vb->v4l2_buf, offsetof(struct v4l2_buffer, m));
+        b->input = vb->v4l2_buf.input;
+        b->reserved = vb->v4l2_buf.reserved;
+
+        if (V4L2_TYPE_IS_MULTIPLANAR(q->type)) {
+                ret = __verify_planes_array(vb, b);
+                if (ret)
+                        return ret;
+
+                /*
+                 * Fill in plane-related data if userspace provided an array
+                 * for it. The memory and size is verified above.
+                 */
+                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_DEQUEUED:
+                /* nothing */
+                break;
+        }
+
+        if (vb->num_planes_mapped == vb->num_planes)
+                b->flags |= V4L2_BUF_FLAG_MAPPED;
+
+        return ret;
+}
+
+/**
+ * vb2_querybuf() - query video buffer information
+ * @q:          videobuf queue
+ * @b:          buffer struct passed from userspace to vidioc_querybuf handler
+ *              in driver
+ *
+ * Should be called from vidioc_querybuf ioctl handler in driver.
+ * This function will verify the passed v4l2_buffer structure and fill the
+ * relevant information for the userspace.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_querybuf handler in driver.
+ */
+int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
+{
+        struct vb2_buffer *vb;
+
+        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];
+
+        return __fill_v4l2_buffer(vb, b);
+}
+EXPORT_SYMBOL(vb2_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;
+}
+
+/**
+ * __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, plane;
+        struct vb2_buffer *vb;
+
+        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
+                vb = q->bufs[buffer];
+                for (plane = 0; plane < vb->num_planes; ++plane) {
+                        /*
+                         * 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 (call_memop(q, plane, num_users,
+                                        vb->planes[plane].mem_priv) > 1)
+                                return true;
+                }
+        }
+
+        return false;
+}
+
+/**
+ * vb2_reqbufs() - Initiate streaming
+ * @q:          videobuf2 queue
+ * @req:        struct passed from userspace to vidioc_reqbufs handler in driver
+ *
+ * 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_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
+{
+        unsigned int num_buffers, num_planes;
+        unsigned long plane_sizes[VIDEO_MAX_PLANES];
+        int ret = 0;
+
+        if (q->fileio) {
+                dprintk(1, "reqbufs: file io in progress\n");
+                return -EBUSY;
+        }
+
+        if (req->memory != V4L2_MEMORY_MMAP
+                        && req->memory != V4L2_MEMORY_USERPTR) {
+                dprintk(1, "reqbufs: unsupported memory type\n");
+                return -EINVAL;
+        }
+
+        if (req->type != q->type) {
+                dprintk(1, "reqbufs: requested type is incorrect\n");
+                return -EINVAL;
+        }
+
+        if (q->streaming) {
+                dprintk(1, "reqbufs: streaming active\n");
+                return -EBUSY;
+        }
+
+        /*
+         * Make sure all the required memory ops for given memory type
+         * are available.
+         */
+        if (req->memory == V4L2_MEMORY_MMAP && __verify_mmap_ops(q)) {
+                dprintk(1, "reqbufs: MMAP for current setup unsupported\n");
+                return -EINVAL;
+        }
+
+        if (req->memory == V4L2_MEMORY_USERPTR && __verify_userptr_ops(q)) {
+                dprintk(1, "reqbufs: USERPTR for current setup unsupported\n");
+                return -EINVAL;
+        }
+
+        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);
+
+                /*
+                 * 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(plane_sizes, 0, sizeof(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, &num_buffers, &num_planes,
+                       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,
+                                plane_sizes);
+        if (ret == 0) {
+                dprintk(1, "Memory allocation failed\n");
+                return -ENOMEM;
+        }
+
+        /*
+         * Check if driver can handle the allocated number of buffers.
+         */
+        if (ret < num_buffers) {
+                unsigned int orig_num_buffers;
+
+                orig_num_buffers = num_buffers = ret;
+                ret = call_qop(q, queue_setup, q, &num_buffers, &num_planes,
+                               plane_sizes, q->alloc_ctx);
+                if (ret)
+                        goto free_mem;
+
+                if (orig_num_buffers < num_buffers) {
+                        ret = -ENOMEM;
+                        goto free_mem;
+                }
+
+                /*
+                 * Ok, driver accepted smaller number of buffers.
+                 */
+                ret = num_buffers;
+        }
+
+        /*
+         * Return the number of successfully allocated buffers
+         * to the userspace.
+         */
+        req->count = ret;
+
+        return 0;
+
+free_mem:
+        __vb2_queue_free(q);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_reqbufs);
+
+/**
+ * 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)
+{
+        struct vb2_queue *q = vb->vb2_queue;
+
+        if (plane_no > vb->num_planes)
+                return NULL;
+
+        return call_memop(q, plane_no, 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)
+{
+        struct vb2_queue *q = vb->vb2_queue;
+
+        if (plane_no > vb->num_planes)
+                return NULL;
+
+        return call_memop(q, plane_no, 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
+ *              or VB2_BUF_STATE_ERROR if the operation finished with an error
+ *
+ * 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.
+ */
+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);
+
+/**
+ * __fill_vb2_buffer() - fill a vb2_buffer with information provided in
+ * a v4l2_buffer by the userspace
+ */
+static int __fill_vb2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b,
+                                struct v4l2_plane *v4l2_planes)
+{
+        unsigned int plane;
+        int ret;
+
+        if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
+                /*
+                 * Verify that the userspace gave us a valid array for
+                 * plane information.
+                 */
+                ret = __verify_planes_array(vb, b);
+                if (ret)
+                        return ret;
+
+                /* 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.input = b->input;
+        vb->v4l2_buf.flags = b->flags & ~V4L2_BUFFER_STATE_FLAGS;
+
+        return 0;
+}
+
+/**
+ * __qbuf_userptr() - handle qbuf of a USERPTR buffer
+ */
+static int __qbuf_userptr(struct vb2_buffer *vb, 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);
+
+        /* Verify and copy relevant information provided by the userspace */
+        ret = __fill_vb2_buffer(vb, b, planes);
+        if (ret)
+                return ret;
+
+        for (plane = 0; plane < vb->num_planes; ++plane) {
+                /* Skip the plane if already verified */
+                if (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);
+
+                /* Release previously acquired memory if present */
+                if (vb->planes[plane].mem_priv)
+                        call_memop(q, plane, put_userptr,
+                                        vb->planes[plane].mem_priv);
+
+                vb->planes[plane].mem_priv = NULL;
+
+                /* Acquire each plane's memory */
+                if (q->mem_ops->get_userptr) {
+                        mem_priv = q->mem_ops->get_userptr(q->alloc_ctx[plane],
+                                                        planes[plane].m.userptr,
+                                                        planes[plane].length,
+                                                        write);
+                        if (IS_ERR(mem_priv)) {
+                                dprintk(1, "qbuf: failed acquiring userspace "
+                                                "memory for plane %d\n", plane);
+                                ret = PTR_ERR(mem_priv);
+                                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) {
+                call_memop(q, plane, put_userptr,
+                                vb->planes[plane - 1].mem_priv);
+                vb->planes[plane - 1].mem_priv = NULL;
+        }
+
+        return ret;
+}
+
+/**
+ * __qbuf_mmap() - handle qbuf of an MMAP buffer
+ */
+static int __qbuf_mmap(struct vb2_buffer *vb, struct v4l2_buffer *b)
+{
+        return __fill_vb2_buffer(vb, b, vb->v4l2_planes);
+}
+
+/**
+ * __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;
+
+        vb->state = VB2_BUF_STATE_ACTIVE;
+        atomic_inc(&q->queued_count);
+        q->ops->buf_queue(vb);
+}
+
+/**
+ * vb2_qbuf() - Queue a buffer from userspace
+ * @q:          videobuf2 queue
+ * @b:          buffer structure passed from userspace to vidioc_qbuf handler
+ *              in driver
+ *
+ * Should be called from vidioc_qbuf ioctl handler of a driver.
+ * This function:
+ * 1) verifies the passed buffer,
+ * 2) calls buf_prepare callback in the driver (if provided), in which
+ *    driver-specific buffer initialization can be performed,
+ * 3) 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_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
+{
+        struct vb2_buffer *vb;
+        int ret = 0;
+
+        if (q->fileio) {
+                dprintk(1, "qbuf: file io in progress\n");
+                return -EBUSY;
+        }
+
+        if (b->type != q->type) {
+                dprintk(1, "qbuf: invalid buffer type\n");
+                return -EINVAL;
+        }
+
+        if (b->index >= q->num_buffers) {
+                dprintk(1, "qbuf: buffer index out of range\n");
+                return -EINVAL;
+        }
+
+        vb = q->bufs[b->index];
+        if (NULL == vb) {
+                /* Should never happen */
+                dprintk(1, "qbuf: buffer is NULL\n");
+                return -EINVAL;
+        }
+
+        if (b->memory != q->memory) {
+                dprintk(1, "qbuf: invalid memory type\n");
+                return -EINVAL;
+        }
+
+        if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+                dprintk(1, "qbuf: buffer already in use\n");
+                return -EINVAL;
+        }
+
+        if (q->memory == V4L2_MEMORY_MMAP)
+                ret = __qbuf_mmap(vb, b);
+        else if (q->memory == V4L2_MEMORY_USERPTR)
+                ret = __qbuf_userptr(vb, b);
+        else {
+                WARN(1, "Invalid queue type\n");
+                return -EINVAL;
+        }
+
+        if (ret)
+                return ret;
+
+        ret = call_qop(q, buf_prepare, vb);
+        if (ret) {
+                dprintk(1, "qbuf: buffer preparation failed\n");
+                return ret;
+        }
+
+        /*
+         * 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);
+
+        dprintk(1, "qbuf of buffer %d succeeded\n", vb->v4l2_buf.index);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_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 (!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)
+                        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,
+                                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);
+        list_del(&(*vb)->done_entry);
+        spin_unlock_irqrestore(&q->done_lock, flags);
+
+        return 0;
+}
+
+/**
+ * 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;
+        }
+
+        wait_event(q->done_wq, !atomic_read(&q->queued_count));
+        return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_wait_for_all_buffers);
+
+/**
+ * vb2_dqbuf() - Dequeue a buffer to the userspace
+ * @q:          videobuf2 queue
+ * @b:          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.
+ * This function:
+ * 1) verifies the passed buffer,
+ * 2) 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,
+ * 3) 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_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, nonblocking);
+        if (ret < 0) {
+                dprintk(1, "dqbuf: error getting next done buffer\n");
+                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);
+
+/**
+ * vb2_streamon - start streaming
+ * @q:          videobuf2 queue
+ * @type:       type argument passed from userspace to vidioc_streamon handler
+ *
+ * Should be called from vidioc_streamon handler of a driver.
+ * This function:
+ * 1) verifies current state
+ * 2) starts streaming and passes any previously queued buffers to the driver
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_streamon handler in the driver.
+ */
+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;
+        }
+
+        /*
+         * Cannot start streaming on an OUTPUT device if no buffers have
+         * been queued yet.
+         */
+        if (V4L2_TYPE_IS_OUTPUT(q->type)) {
+                if (list_empty(&q->queued_list)) {
+                        dprintk(1, "streamon: no output buffers queued\n");
+                        return -EINVAL;
+                }
+        }
+
+        /*
+         * Let driver notice that streaming state has been enabled.
+         */
+        ret = call_qop(q, start_streaming, q);
+        if (ret) {
+                dprintk(1, "streamon: driver refused to start streaming\n");
+                return ret;
+        }
+
+        q->streaming = 1;
+
+        /*
+         * 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);
+
+        dprintk(3, "Streamon successful\n");
+        return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_streamon);
+
+/**
+ * __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->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;
+}
+
+/**
+ * vb2_streamoff - stop streaming
+ * @q:          videobuf2 queue
+ * @type:       type argument passed from userspace to vidioc_streamoff handler
+ *
+ * Should be called from vidioc_streamoff handler of a driver.
+ * This function:
+ * 1) verifies current state,
+ * 2) stop streaming and dequeues any queued buffers, including those previously
+ *    passed to the driver (after waiting for the driver to finish).
+ *
+ * This call can be used for pausing playback.
+ * The return values from this function are intended to be directly returned
+ * from vidioc_streamoff handler in the driver
+ */
+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);
+
+/**
+ * __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->v4l2_planes[plane].m.mem_offset == off) {
+                                *_buffer = buffer;
+                                *_plane = plane;
+                                return 0;
+                        }
+                }
+        }
+
+        return -EINVAL;
+}
+
+/**
+ * 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_plane *vb_plane;
+        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];
+        vb_plane = &vb->planes[plane];
+
+        ret = q->mem_ops->mmap(vb_plane->mem_priv, vma);
+        if (ret)
+                return ret;
+
+        vb_plane->mapped = 1;
+        vb->num_planes_mapped++;
+
+        dprintk(3, "Buffer %d, plane %d successfully mapped\n", buffer, plane);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_mmap);
+
+static int __vb2_init_fileio(struct vb2_queue *q, int read);
+static int __vb2_cleanup_fileio(struct vb2_queue *q);
+
+/**
+ * vb2_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_poll(struct vb2_queue *q, struct file *file, poll_table *wait)
+{
+        unsigned long flags;
+        unsigned int ret;
+        struct vb2_buffer *vb = NULL;
+
+        /*
+         * 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)) {
+                        ret = __vb2_init_fileio(q, 1);
+                        if (ret)
+                                return POLLERR;
+                }
+                if (V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_WRITE)) {
+                        ret = __vb2_init_fileio(q, 0);
+                        if (ret)
+                                return POLLERR;
+                        /*
+                         * Write to OUTPUT queue can be done immediately.
+                         */
+                        return POLLOUT | POLLWRNORM;
+                }
+        }
+
+        /*
+         * There is nothing to wait for if no buffers have already been queued.
+         */
+        if (list_empty(&q->queued_list))
+                return 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)) ? POLLOUT | POLLWRNORM :
+                        POLLIN | POLLRDNORM;
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_poll);
+
+/**
+ * vb2_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_queue_init(struct vb2_queue *q)
+{
+        BUG_ON(!q);
+        BUG_ON(!q->ops);
+        BUG_ON(!q->mem_ops);
+        BUG_ON(!q->type);
+        BUG_ON(!q->io_modes);
+
+        BUG_ON(!q->ops->queue_setup);
+        BUG_ON(!q->ops->buf_queue);
+
+        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);
+
+/**
+ * vb2_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_queue_release(struct vb2_queue *q)
+{
+        __vb2_cleanup_fileio(q);
+        __vb2_queue_cancel(q);
+        __vb2_queue_free(q);
+}
+EXPORT_SYMBOL_GPL(vb2_queue_release);
+
+/**
+ * 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
+ *
+ * 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 {
+        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;
+};
+
+/**
+ * __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 ((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) {
+                fileio->req.count = 0;
+                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:
+        vb2_reqbufs(q, &fileio->req);
+
+err_kfree:
+        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) {
+                /*
+                 * 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;
+}
+
+/**
+ * __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;
+        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);
+
+MODULE_DESCRIPTION("Driver helper framework for Video for Linux 2");
+MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>, Marek Szyprowski");
+MODULE_LICENSE("GPL");