linux_dsm_epyc7002/drivers/media/video/videobuf2-core.c

/*
 * 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/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)

/**
 * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
 */
static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
{
	struct vb2_queue *q = vb->vb2_queue;
	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;
}

/**
 * __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, 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) {
		if (vb->planes[plane].mem_priv)
			call_memop(q, put_userptr, vb->planes[plane].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 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);
		}
	}
}

/**
 * __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 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;
}

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

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

		/* Free MMAP buffers or release USERPTR buffers */
		if (q->memory == V4L2_MEMORY_MMAP)
			__vb2_buf_mem_free(vb);
		else
			__vb2_buf_userptr_put(vb);
	}
}

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

/**
 * __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, const 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;
}

/**
 * __buffer_in_use() - return true if the buffer is in use and
 * the queue cannot be freed (by the means of REQBUFS(0)) call
 */
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;
}

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

/**
 * __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;

	/* 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)) {
		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_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;

	return 0;
}

/**
 * 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;
}

/**
 * __verify_memory_type() - Check whether the memory type and buffer type
 * passed to a buffer operation are compatible with the queue.
 */
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;
}

/**
 * __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.
 */
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;
}

/**
 * vb2_reqbufs() - Wrapper for __reqbufs() that also verifies the memory and
 * type values.
 * @q:		videobuf2 queue
 * @req:	struct passed from userspace to vidioc_reqbufs handler in driver
 */
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);

/**
 * __create_bufs() - Allocate buffers and any required auxiliary structs
 * @q:		videobuf2 queue
 * @create:	creation parameters, passed from userspace to vidioc_create_bufs
 *		handler in driver
 *
 * Should be called from vidioc_create_bufs ioctl handler of a driver.
 * This function:
 * 1) verifies parameter sanity
 * 2) calls the .queue_setup() queue operation
 * 3) performs any necessary memory allocations
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_create_bufs handler in driver.
 */
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;
}

/**
 * vb2_create_bufs() - Wrapper for __create_bufs() that also verifies the
 * memory and type values.
 * @q:		videobuf2 queue
 * @create:	creation parameters, passed from userspace to vidioc_create_bufs
 *		handler in driver
 */
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);

/**
 * 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 || !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);

/**
 * 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 || !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);

/**
 * 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, const 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.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, 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);

	/* 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 &&
		    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;
}

/**
 * __qbuf_mmap() - handle qbuf of an MMAP buffer
 */
static int __qbuf_mmap(struct vb2_buffer *vb, const 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);
}

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;
}

/**
 * vb2_prepare_buf() - Pass ownership of a buffer from userspace to the kernel
 * @q:		videobuf2 queue
 * @b:		buffer structure passed from userspace to vidioc_prepare_buf
 *		handler in driver
 *
 * Should be called from vidioc_prepare_buf 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,
 *
 * The return values from this function are intended to be directly returned
 * from vidioc_prepare_buf handler in driver.
 */
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 = __buf_prepare(vb, b);
	if (ret < 0)
		return ret;

	__fill_v4l2_buffer(vb, b);

	return 0;
}
EXPORT_SYMBOL_GPL(vb2_prepare_buf);

/**
 * 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) if necessary, 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 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;
	}

	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);

/**
 * __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_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_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) passes any previously queued buffers to the driver and starts streaming
 *
 * 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;
	}

	/*
	 * 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);


/**
 * 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_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);

/**
 * 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.
 *
 * If the driver uses struct v4l2_fh, then vb2_poll() will also check for any
 * pending events.
 *
 * 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)
{
	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);

/**
 * 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, q->num_buffers);
}
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) {
		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;
}

/**
 * __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);


/*
 * 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;
	bool must_lock = !test_bit(V4L2_FL_LOCK_ALL_FOPS, &vdev->flags) && lock;
	int err = -EBUSY;

	if (must_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 (err >= 0)
		vdev->queue->owner = file->private_data;
exit:
	if (must_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;
	bool must_lock = !test_bit(V4L2_FL_LOCK_ALL_FOPS, &vdev->flags) && vdev->lock;
	int err = -EBUSY;

	if (must_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 (err >= 0)
		vdev->queue->owner = file->private_data;
exit:
	if (must_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;
	/* Yuck. We really need to get rid of this flag asap. If it is
	   set, then the core took the serialization lock before calling
	   poll(). This is being phased out, but for now we have to handle
	   this case. */
	bool locked = test_bit(V4L2_FL_LOCK_ALL_FOPS, &vdev->flags);
	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 && !locked && !lock);

	if (must_lock && !locked && 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 && !locked && 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 <pawel@osciak.com>, Marek Szyprowski");
MODULE_LICENSE("GPL");