Initial import

1 files changed, 3552 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
new file mode 100644
index 000000000..cf9d644a8
--- /dev/null
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -0,0 +1,3552 @@
+/*
+ * videobuf2-core.c - V4L2 driver helper framework
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ *
+ * Author: Pawel Osciak <pawel@osciak.com>
+ *	   Marek Szyprowski <m.szyprowski@samsung.com>
+ *
+ * The vb2_thread implementation was based on code from videobuf-dvb.c:
+ *	(c) 2004 Gerd Knorr <kraxel@bytesex.org> [SUSE Labs]
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+
+#include <media/v4l2-dev.h>
+#include <media/v4l2-fh.h>
+#include <media/v4l2-event.h>
+#include <media/v4l2-common.h>
+#include <media/videobuf2-core.h>
+
+static int debug;
+module_param(debug, int, 0644);
+
+#define dprintk(level, fmt, arg...)					      \
+	do {								      \
+		if (debug >= level)					      \
+			pr_info("vb2: %s: " fmt, __func__, ## arg); \
+	} while (0)
+
+#ifdef CONFIG_VIDEO_ADV_DEBUG
+
+/*
+ * If advanced debugging is on, then count how often each op is called
+ * successfully, which can either be per-buffer or per-queue.
+ *
+ * This makes it easy to check that the 'init' and 'cleanup'
+ * (and variations thereof) stay balanced.
+ */
+
+#define log_memop(vb, op)						\
+	dprintk(2, "call_memop(%p, %d, %s)%s\n",			\
+		(vb)->vb2_queue, (vb)->v4l2_buf.index, #op,		\
+		(vb)->vb2_queue->mem_ops->op ? "" : " (nop)")
+
+#define call_memop(vb, op, args...)					\
+({									\
+	struct vb2_queue *_q = (vb)->vb2_queue;				\
+	int err;							\
+									\
+	log_memop(vb, op);						\
+	err = _q->mem_ops->op ? _q->mem_ops->op(args) : 0;		\
+	if (!err)							\
+		(vb)->cnt_mem_ ## op++;					\
+	err;								\
+})
+
+#define call_ptr_memop(vb, op, args...)					\
+({									\
+	struct vb2_queue *_q = (vb)->vb2_queue;				\
+	void *ptr;							\
+									\
+	log_memop(vb, op);						\
+	ptr = _q->mem_ops->op ? _q->mem_ops->op(args) : NULL;		\
+	if (!IS_ERR_OR_NULL(ptr))					\
+		(vb)->cnt_mem_ ## op++;					\
+	ptr;								\
+})
+
+#define call_void_memop(vb, op, args...)				\
+({									\
+	struct vb2_queue *_q = (vb)->vb2_queue;				\
+									\
+	log_memop(vb, op);						\
+	if (_q->mem_ops->op)						\
+		_q->mem_ops->op(args);					\
+	(vb)->cnt_mem_ ## op++;						\
+})
+
+#define log_qop(q, op)							\
+	dprintk(2, "call_qop(%p, %s)%s\n", q, #op,			\
+		(q)->ops->op ? "" : " (nop)")
+
+#define call_qop(q, op, args...)					\
+({									\
+	int err;							\
+									\
+	log_qop(q, op);							\
+	err = (q)->ops->op ? (q)->ops->op(args) : 0;			\
+	if (!err)							\
+		(q)->cnt_ ## op++;					\
+	err;								\
+})
+
+#define call_void_qop(q, op, args...)					\
+({									\
+	log_qop(q, op);							\
+	if ((q)->ops->op)						\
+		(q)->ops->op(args);					\
+	(q)->cnt_ ## op++;						\
+})
+
+#define log_vb_qop(vb, op, args...)					\
+	dprintk(2, "call_vb_qop(%p, %d, %s)%s\n",			\
+		(vb)->vb2_queue, (vb)->v4l2_buf.index, #op,		\
+		(vb)->vb2_queue->ops->op ? "" : " (nop)")
+
+#define call_vb_qop(vb, op, args...)					\
+({									\
+	int err;							\
+									\
+	log_vb_qop(vb, op);						\
+	err = (vb)->vb2_queue->ops->op ?				\
+		(vb)->vb2_queue->ops->op(args) : 0;			\
+	if (!err)							\
+		(vb)->cnt_ ## op++;					\
+	err;								\
+})
+
+#define call_void_vb_qop(vb, op, args...)				\
+({									\
+	log_vb_qop(vb, op);						\
+	if ((vb)->vb2_queue->ops->op)					\
+		(vb)->vb2_queue->ops->op(args);				\
+	(vb)->cnt_ ## op++;						\
+})
+
+#else
+
+#define call_memop(vb, op, args...)					\
+	((vb)->vb2_queue->mem_ops->op ?					\
+		(vb)->vb2_queue->mem_ops->op(args) : 0)
+
+#define call_ptr_memop(vb, op, args...)					\
+	((vb)->vb2_queue->mem_ops->op ?					\
+		(vb)->vb2_queue->mem_ops->op(args) : NULL)
+
+#define call_void_memop(vb, op, args...)				\
+	do {								\
+		if ((vb)->vb2_queue->mem_ops->op)			\
+			(vb)->vb2_queue->mem_ops->op(args);		\
+	} while (0)
+
+#define call_qop(q, op, args...)					\
+	((q)->ops->op ? (q)->ops->op(args) : 0)
+
+#define call_void_qop(q, op, args...)					\
+	do {								\
+		if ((q)->ops->op)					\
+			(q)->ops->op(args);				\
+	} while (0)
+
+#define call_vb_qop(vb, op, args...)					\
+	((vb)->vb2_queue->ops->op ? (vb)->vb2_queue->ops->op(args) : 0)
+
+#define call_void_vb_qop(vb, op, args...)				\
+	do {								\
+		if ((vb)->vb2_queue->ops->op)				\
+			(vb)->vb2_queue->ops->op(args);			\
+	} while (0)
+
+#endif
+
+/* Flags that are set by the vb2 core */
+#define V4L2_BUFFER_MASK_FLAGS	(V4L2_BUF_FLAG_MAPPED | V4L2_BUF_FLAG_QUEUED | \
+				 V4L2_BUF_FLAG_DONE | V4L2_BUF_FLAG_ERROR | \
+				 V4L2_BUF_FLAG_PREPARED | \
+				 V4L2_BUF_FLAG_TIMESTAMP_MASK)
+/* Output buffer flags that should be passed on to the driver */
+#define V4L2_BUFFER_OUT_FLAGS	(V4L2_BUF_FLAG_PFRAME | V4L2_BUF_FLAG_BFRAME | \
+				 V4L2_BUF_FLAG_KEYFRAME | V4L2_BUF_FLAG_TIMECODE)
+
+static void __vb2_queue_cancel(struct vb2_queue *q);
+
+/**
+ * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
+ */
+static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+	enum dma_data_direction dma_dir =
+		V4L2_TYPE_IS_OUTPUT(q->type) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	void *mem_priv;
+	int plane;
+
+	/*
+	 * Allocate memory for all planes in this buffer
+	 * NOTE: mmapped areas should be page aligned
+	 */
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		unsigned long size = PAGE_ALIGN(q->plane_sizes[plane]);
+
+		mem_priv = call_ptr_memop(vb, alloc, q->alloc_ctx[plane],
+				      size, dma_dir, q->gfp_flags);
+		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_void_memop(vb, 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)
+{
+	unsigned int plane;
+
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		call_void_memop(vb, put, vb->planes[plane].mem_priv);
+		vb->planes[plane].mem_priv = NULL;
+		dprintk(3, "freed plane %d of buffer %d\n", plane,
+			vb->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)
+{
+	unsigned int plane;
+
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		if (vb->planes[plane].mem_priv)
+			call_void_memop(vb, put_userptr, vb->planes[plane].mem_priv);
+		vb->planes[plane].mem_priv = NULL;
+	}
+}
+
+/**
+ * __vb2_plane_dmabuf_put() - release memory associated with
+ * a DMABUF shared plane
+ */
+static void __vb2_plane_dmabuf_put(struct vb2_buffer *vb, struct vb2_plane *p)
+{
+	if (!p->mem_priv)
+		return;
+
+	if (p->dbuf_mapped)
+		call_void_memop(vb, unmap_dmabuf, p->mem_priv);
+
+	call_void_memop(vb, detach_dmabuf, p->mem_priv);
+	dma_buf_put(p->dbuf);
+	memset(p, 0, sizeof(*p));
+}
+
+/**
+ * __vb2_buf_dmabuf_put() - release memory associated with
+ * a DMABUF shared buffer
+ */
+static void __vb2_buf_dmabuf_put(struct vb2_buffer *vb)
+{
+	unsigned int plane;
+
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		__vb2_plane_dmabuf_put(vb, &vb->planes[plane]);
+}
+
+/**
+ * __setup_lengths() - setup initial lengths for every plane in
+ * every buffer on the queue
+ */
+static void __setup_lengths(struct vb2_queue *q, unsigned int n)
+{
+	unsigned int buffer, plane;
+	struct vb2_buffer *vb;
+
+	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];
+	}
+}
+
+/**
+ * __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].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_vb_qop(vb, 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_lengths(q, buffer);
+	if (memory == V4L2_MEMORY_MMAP)
+		__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 if (q->memory == V4L2_MEMORY_DMABUF)
+			__vb2_buf_dmabuf_put(vb);
+		else
+			__vb2_buf_userptr_put(vb);
+	}
+}
+
+/**
+ * __vb2_queue_free() - free buffers at the end of the queue - video memory and
+ * related information, if no buffers are left return the queue to an
+ * uninitialized state. Might be called even if the queue has already been freed.
+ */
+static int __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
+{
+	unsigned int buffer;
+
+	/*
+	 * Sanity check: when preparing a buffer the queue lock is released for
+	 * a short while (see __buf_prepare for the details), which would allow
+	 * a race with a reqbufs which can call this function. Removing the
+	 * buffers from underneath __buf_prepare is obviously a bad idea, so we
+	 * check if any of the buffers is in the state PREPARING, and if so we
+	 * just return -EAGAIN.
+	 */
+	for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
+	     ++buffer) {
+		if (q->bufs[buffer] == NULL)
+			continue;
+		if (q->bufs[buffer]->state == VB2_BUF_STATE_PREPARING) {
+			dprintk(1, "preparing buffers, cannot free\n");
+			return -EAGAIN;
+		}
+	}
+
+	/* Call driver-provided cleanup function for each buffer, if provided */
+	for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
+	     ++buffer) {
+		struct vb2_buffer *vb = q->bufs[buffer];
+
+		if (vb && vb->planes[0].mem_priv)
+			call_void_vb_qop(vb, buf_cleanup, vb);
+	}
+
+	/* Release video buffer memory */
+	__vb2_free_mem(q, buffers);
+
+#ifdef CONFIG_VIDEO_ADV_DEBUG
+	/*
+	 * Check that all the calls were balances during the life-time of this
+	 * queue. If not (or if the debug level is 1 or up), then dump the
+	 * counters to the kernel log.
+	 */
+	if (q->num_buffers) {
+		bool unbalanced = q->cnt_start_streaming != q->cnt_stop_streaming ||
+				  q->cnt_wait_prepare != q->cnt_wait_finish;
+
+		if (unbalanced || debug) {
+			pr_info("vb2: counters for queue %p:%s\n", q,
+				unbalanced ? " UNBALANCED!" : "");
+			pr_info("vb2:     setup: %u start_streaming: %u stop_streaming: %u\n",
+				q->cnt_queue_setup, q->cnt_start_streaming,
+				q->cnt_stop_streaming);
+			pr_info("vb2:     wait_prepare: %u wait_finish: %u\n",
+				q->cnt_wait_prepare, q->cnt_wait_finish);
+		}
+		q->cnt_queue_setup = 0;
+		q->cnt_wait_prepare = 0;
+		q->cnt_wait_finish = 0;
+		q->cnt_start_streaming = 0;
+		q->cnt_stop_streaming = 0;
+	}
+	for (buffer = 0; buffer < q->num_buffers; ++buffer) {
+		struct vb2_buffer *vb = q->bufs[buffer];
+		bool unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
+				  vb->cnt_mem_prepare != vb->cnt_mem_finish ||
+				  vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
+				  vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
+				  vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
+				  vb->cnt_buf_queue != vb->cnt_buf_done ||
+				  vb->cnt_buf_prepare != vb->cnt_buf_finish ||
+				  vb->cnt_buf_init != vb->cnt_buf_cleanup;
+
+		if (unbalanced || debug) {
+			pr_info("vb2:   counters for queue %p, buffer %d:%s\n",
+				q, buffer, unbalanced ? " UNBALANCED!" : "");
+			pr_info("vb2:     buf_init: %u buf_cleanup: %u buf_prepare: %u buf_finish: %u\n",
+				vb->cnt_buf_init, vb->cnt_buf_cleanup,
+				vb->cnt_buf_prepare, vb->cnt_buf_finish);
+			pr_info("vb2:     buf_queue: %u buf_done: %u\n",
+				vb->cnt_buf_queue, vb->cnt_buf_done);
+			pr_info("vb2:     alloc: %u put: %u prepare: %u finish: %u mmap: %u\n",
+				vb->cnt_mem_alloc, vb->cnt_mem_put,
+				vb->cnt_mem_prepare, vb->cnt_mem_finish,
+				vb->cnt_mem_mmap);
+			pr_info("vb2:     get_userptr: %u put_userptr: %u\n",
+				vb->cnt_mem_get_userptr, vb->cnt_mem_put_userptr);
+			pr_info("vb2:     attach_dmabuf: %u detach_dmabuf: %u map_dmabuf: %u unmap_dmabuf: %u\n",
+				vb->cnt_mem_attach_dmabuf, vb->cnt_mem_detach_dmabuf,
+				vb->cnt_mem_map_dmabuf, vb->cnt_mem_unmap_dmabuf);
+			pr_info("vb2:     get_dmabuf: %u num_users: %u vaddr: %u cookie: %u\n",
+				vb->cnt_mem_get_dmabuf,
+				vb->cnt_mem_num_users,
+				vb->cnt_mem_vaddr,
+				vb->cnt_mem_cookie);
+		}
+	}
+#endif
+
+	/* Free videobuf buffers */
+	for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
+	     ++buffer) {
+		kfree(q->bufs[buffer]);
+		q->bufs[buffer] = NULL;
+	}
+
+	q->num_buffers -= buffers;
+	if (!q->num_buffers) {
+		q->memory = 0;
+		INIT_LIST_HEAD(&q->queued_list);
+	}
+	return 0;
+}
+
+/**
+ * __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)
+{
+	if (!V4L2_TYPE_IS_MULTIPLANAR(b->type))
+		return 0;
+
+	/* Is memory for copying plane information present? */
+	if (NULL == b->m.planes) {
+		dprintk(1, "multi-planar buffer passed but "
+			   "planes array not provided\n");
+		return -EINVAL;
+	}
+
+	if (b->length < vb->num_planes || b->length > VIDEO_MAX_PLANES) {
+		dprintk(1, "incorrect planes array length, "
+			   "expected %d, got %d\n", vb->num_planes, b->length);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * __verify_length() - Verify that the bytesused value for each plane fits in
+ * the plane length and that the data offset doesn't exceed the bytesused value.
+ */
+static int __verify_length(struct vb2_buffer *vb, const struct v4l2_buffer *b)
+{
+	unsigned int length;
+	unsigned int bytesused;
+	unsigned int plane;
+
+	if (!V4L2_TYPE_IS_OUTPUT(b->type))
+		return 0;
+
+	if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
+		for (plane = 0; plane < vb->num_planes; ++plane) {
+			length = (b->memory == V4L2_MEMORY_USERPTR ||
+				  b->memory == V4L2_MEMORY_DMABUF)
+			       ? b->m.planes[plane].length
+			       : vb->v4l2_planes[plane].length;
+			bytesused = b->m.planes[plane].bytesused
+				  ? b->m.planes[plane].bytesused : length;
+
+			if (b->m.planes[plane].bytesused > length)
+				return -EINVAL;
+
+			if (b->m.planes[plane].data_offset > 0 &&
+			    b->m.planes[plane].data_offset >= bytesused)
+				return -EINVAL;
+		}
+	} else {
+		length = (b->memory == V4L2_MEMORY_USERPTR)
+		       ? b->length : vb->v4l2_planes[0].length;
+		bytesused = b->bytesused ? b->bytesused : length;
+
+		if (b->bytesused > 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(vb, 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 void __fill_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+
+	/* Copy back data such as timestamp, flags, etc. */
+	memcpy(b, &vb->v4l2_buf, offsetof(struct v4l2_buffer, m));
+	b->reserved2 = vb->v4l2_buf.reserved2;
+	b->reserved = vb->v4l2_buf.reserved;
+
+	if (V4L2_TYPE_IS_MULTIPLANAR(q->type)) {
+		/*
+		 * Fill in plane-related data if userspace provided an array
+		 * for it. The caller has already verified memory and size.
+		 */
+		b->length = vb->num_planes;
+		memcpy(b->m.planes, vb->v4l2_planes,
+			b->length * sizeof(struct v4l2_plane));
+	} else {
+		/*
+		 * We use length and offset in v4l2_planes array even for
+		 * single-planar buffers, but userspace does not.
+		 */
+		b->length = vb->v4l2_planes[0].length;
+		b->bytesused = vb->v4l2_planes[0].bytesused;
+		if (q->memory == V4L2_MEMORY_MMAP)
+			b->m.offset = vb->v4l2_planes[0].m.mem_offset;
+		else if (q->memory == V4L2_MEMORY_USERPTR)
+			b->m.userptr = vb->v4l2_planes[0].m.userptr;
+		else if (q->memory == V4L2_MEMORY_DMABUF)
+			b->m.fd = vb->v4l2_planes[0].m.fd;
+	}
+
+	/*
+	 * Clear any buffer state related flags.
+	 */
+	b->flags &= ~V4L2_BUFFER_MASK_FLAGS;
+	b->flags |= q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK;
+	if ((q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) !=
+	    V4L2_BUF_FLAG_TIMESTAMP_COPY) {
+		/*
+		 * For non-COPY timestamps, drop timestamp source bits
+		 * and obtain the timestamp source from the queue.
+		 */
+		b->flags &= ~V4L2_BUF_FLAG_TSTAMP_SRC_MASK;
+		b->flags |= q->timestamp_flags & V4L2_BUF_FLAG_TSTAMP_SRC_MASK;
+	}
+
+	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_PREPARING:
+	case VB2_BUF_STATE_DEQUEUED:
+		/* nothing */
+		break;
+	}
+
+	if (__buffer_in_use(q, vb))
+		b->flags |= V4L2_BUF_FLAG_MAPPED;
+}
+
+/**
+ * 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;
+	int ret;
+
+	if (b->type != q->type) {
+		dprintk(1, "wrong buffer type\n");
+		return -EINVAL;
+	}
+
+	if (b->index >= q->num_buffers) {
+		dprintk(1, "buffer index out of range\n");
+		return -EINVAL;
+	}
+	vb = q->bufs[b->index];
+	ret = __verify_planes_array(vb, b);
+	if (!ret)
+		__fill_v4l2_buffer(vb, b);
+	return ret;
+}
+EXPORT_SYMBOL(vb2_querybuf);
+
+/**
+ * __verify_userptr_ops() - verify that all memory operations required for
+ * USERPTR queue type have been provided
+ */
+static int __verify_userptr_ops(struct vb2_queue *q)
+{
+	if (!(q->io_modes & VB2_USERPTR) || !q->mem_ops->get_userptr ||
+	    !q->mem_ops->put_userptr)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * __verify_mmap_ops() - verify that all memory operations required for
+ * MMAP queue type have been provided
+ */
+static int __verify_mmap_ops(struct vb2_queue *q)
+{
+	if (!(q->io_modes & VB2_MMAP) || !q->mem_ops->alloc ||
+	    !q->mem_ops->put || !q->mem_ops->mmap)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * __verify_dmabuf_ops() - verify that all memory operations required for
+ * DMABUF queue type have been provided
+ */
+static int __verify_dmabuf_ops(struct vb2_queue *q)
+{
+	if (!(q->io_modes & VB2_DMABUF) || !q->mem_ops->attach_dmabuf ||
+	    !q->mem_ops->detach_dmabuf  || !q->mem_ops->map_dmabuf ||
+	    !q->mem_ops->unmap_dmabuf)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * __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 &&
+	    memory != V4L2_MEMORY_DMABUF) {
+		dprintk(1, "unsupported memory type\n");
+		return -EINVAL;
+	}
+
+	if (type != q->type) {
+		dprintk(1, "requested type is incorrect\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Make sure all the required memory ops for given memory type
+	 * are available.
+	 */
+	if (memory == V4L2_MEMORY_MMAP && __verify_mmap_ops(q)) {
+		dprintk(1, "MMAP for current setup unsupported\n");
+		return -EINVAL;
+	}
+
+	if (memory == V4L2_MEMORY_USERPTR && __verify_userptr_ops(q)) {
+		dprintk(1, "USERPTR for current setup unsupported\n");
+		return -EINVAL;
+	}
+
+	if (memory == V4L2_MEMORY_DMABUF && __verify_dmabuf_ops(q)) {
+		dprintk(1, "DMABUF for current setup unsupported\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Place the busy tests at the end: -EBUSY can be ignored when
+	 * create_bufs is called with count == 0, but count == 0 should still
+	 * do the memory and type validation.
+	 */
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+	return 0;
+}
+
+/**
+ * __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, "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.
+		 */
+		mutex_lock(&q->mmap_lock);
+		if (q->memory == V4L2_MEMORY_MMAP && __buffers_in_use(q)) {
+			mutex_unlock(&q->mmap_lock);
+			dprintk(1, "memory in use, cannot free\n");
+			return -EBUSY;
+		}
+
+		/*
+		 * Call queue_cancel to clean up any buffers in the PREPARED or
+		 * QUEUED state which is possible if buffers were prepared or
+		 * queued without ever calling STREAMON.
+		 */
+		__vb2_queue_cancel(q);
+		ret = __vb2_queue_free(q, q->num_buffers);
+		mutex_unlock(&q->mmap_lock);
+		if (ret)
+			return ret;
+
+		/*
+		 * In case of REQBUFS(0) return immediately without calling
+		 * driver's queue_setup() callback and allocating resources.
+		 */
+		if (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);
+	num_buffers = max_t(unsigned int, num_buffers, q->min_buffers_needed);
+	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 */
+	allocated_buffers = __vb2_queue_alloc(q, req->memory, num_buffers, num_planes);
+	if (allocated_buffers == 0) {
+		dprintk(1, "memory allocation failed\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * There is no point in continuing if we can't allocate the minimum
+	 * number of buffers needed by this vb2_queue.
+	 */
+	if (allocated_buffers < q->min_buffers_needed)
+		ret = -ENOMEM;
+
+	/*
+	 * Check if driver can handle the allocated number of buffers.
+	 */
+	if (!ret && allocated_buffers < num_buffers) {
+		num_buffers = allocated_buffers;
+
+		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
+		 */
+	}
+
+	mutex_lock(&q->mmap_lock);
+	q->num_buffers = allocated_buffers;
+
+	if (ret < 0) {
+		/*
+		 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
+		 * from q->num_buffers.
+		 */
+		__vb2_queue_free(q, allocated_buffers);
+		mutex_unlock(&q->mmap_lock);
+		return ret;
+	}
+	mutex_unlock(&q->mmap_lock);
+
+	/*
+	 * Return the number of successfully allocated buffers
+	 * to the userspace.
+	 */
+	req->count = allocated_buffers;
+	q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
+
+	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, "maximum number of buffers already allocated\n");
+		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;
+		q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
+	}
+
+	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 */
+	allocated_buffers = __vb2_queue_alloc(q, create->memory, num_buffers,
+				num_planes);
+	if (allocated_buffers == 0) {
+		dprintk(1, "memory allocation failed\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * Check if driver can handle the so far allocated number of buffers.
+	 */
+	if (allocated_buffers < num_buffers) {
+		num_buffers = allocated_buffers;
+
+		/*
+		 * q->num_buffers contains the total number of buffers, that the
+		 * queue driver has set up
+		 */
+		ret = call_qop(q, queue_setup, q, &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
+		 */
+	}
+
+	mutex_lock(&q->mmap_lock);
+	q->num_buffers += allocated_buffers;
+
+	if (ret < 0) {
+		/*
+		 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
+		 * from q->num_buffers.
+		 */
+		__vb2_queue_free(q, allocated_buffers);
+		mutex_unlock(&q->mmap_lock);
+		return -ENOMEM;
+	}
+	mutex_unlock(&q->mmap_lock);
+
+	/*
+	 * Return the number of successfully allocated buffers
+	 * to the userspace.
+	 */
+	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)
+{
+	if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
+		return NULL;
+
+	return call_ptr_memop(vb, vaddr, vb->planes[plane_no].mem_priv);
+
+}
+EXPORT_SYMBOL_GPL(vb2_plane_vaddr);
+
+/**
+ * vb2_plane_cookie() - Return allocator specific cookie for the given plane
+ * @vb:		vb2_buffer to which the plane in question belongs to
+ * @plane_no:	plane number for which the cookie is to be returned
+ *
+ * This function returns an allocator specific cookie for a given plane if
+ * available, NULL otherwise. The allocator should provide some simple static
+ * inline function, which would convert this cookie to the allocator specific
+ * type that can be used directly by the driver to access the buffer. This can
+ * be for example physical address, pointer to scatter list or IOMMU mapping.
+ */
+void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
+{
+	if (plane_no >= vb->num_planes || !vb->planes[plane_no].mem_priv)
+		return NULL;
+
+	return call_ptr_memop(vb, cookie, vb->planes[plane_no].mem_priv);
+}
+EXPORT_SYMBOL_GPL(vb2_plane_cookie);
+
+/**
+ * vb2_buffer_done() - inform videobuf that an operation on a buffer is finished
+ * @vb:		vb2_buffer returned from the driver
+ * @state:	either VB2_BUF_STATE_DONE if the operation finished successfully
+ *		or VB2_BUF_STATE_ERROR if the operation finished with an error.
+ *		If start_streaming fails then it should return buffers with state
+ *		VB2_BUF_STATE_QUEUED to put them back into the queue.
+ *
+ * This function should be called by the driver after a hardware operation on
+ * a buffer is finished and the buffer may be returned to userspace. The driver
+ * cannot use this buffer anymore until it is queued back to it by videobuf
+ * by the means of buf_queue callback. Only buffers previously queued to the
+ * driver by buf_queue can be passed to this function.
+ *
+ * While streaming a buffer can only be returned in state DONE or ERROR.
+ * The start_streaming op can also return them in case the DMA engine cannot
+ * be started for some reason. In that case the buffers should be returned with
+ * state QUEUED.
+ */
+void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+	unsigned long flags;
+	unsigned int plane;
+
+	if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
+		return;
+
+	if (WARN_ON(state != VB2_BUF_STATE_DONE &&
+		    state != VB2_BUF_STATE_ERROR &&
+		    state != VB2_BUF_STATE_QUEUED))
+		state = VB2_BUF_STATE_ERROR;
+
+#ifdef CONFIG_VIDEO_ADV_DEBUG
+	/*
+	 * Although this is not a callback, it still does have to balance
+	 * with the buf_queue op. So update this counter manually.
+	 */
+	vb->cnt_buf_done++;
+#endif
+	dprintk(4, "done processing on buffer %d, state: %d\n",
+			vb->v4l2_buf.index, state);
+
+	/* sync buffers */
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		call_void_memop(vb, finish, vb->planes[plane].mem_priv);
+
+	/* Add the buffer to the done buffers list */
+	spin_lock_irqsave(&q->done_lock, flags);
+	vb->state = state;
+	if (state != VB2_BUF_STATE_QUEUED)
+		list_add_tail(&vb->done_entry, &q->done_list);
+	atomic_dec(&q->owned_by_drv_count);
+	spin_unlock_irqrestore(&q->done_lock, flags);
+
+	if (state == VB2_BUF_STATE_QUEUED)
+		return;
+
+	/* Inform any processes that may be waiting for buffers */
+	wake_up(&q->done_wq);
+}
+EXPORT_SYMBOL_GPL(vb2_buffer_done);
+
+/**
+ * vb2_discard_done() - discard all buffers marked as DONE
+ * @q:		videobuf2 queue
+ *
+ * This function is intended to be used with suspend/resume operations. It
+ * discards all 'done' buffers as they would be too old to be requested after
+ * resume.
+ *
+ * Drivers must stop the hardware and synchronize with interrupt handlers and/or
+ * delayed works before calling this function to make sure no buffer will be
+ * touched by the driver and/or hardware.
+ */
+void vb2_discard_done(struct vb2_queue *q)
+{
+	struct vb2_buffer *vb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&q->done_lock, flags);
+	list_for_each_entry(vb, &q->done_list, done_entry)
+		vb->state = VB2_BUF_STATE_ERROR;
+	spin_unlock_irqrestore(&q->done_lock, flags);
+}
+EXPORT_SYMBOL_GPL(vb2_discard_done);
+
+static void vb2_warn_zero_bytesused(struct vb2_buffer *vb)
+{
+	static bool __check_once __read_mostly;
+
+	if (__check_once)
+		return;
+
+	__check_once = true;
+	__WARN();
+
+	pr_warn_once("use of bytesused == 0 is deprecated and will be removed in the future,\n");
+	if (vb->vb2_queue->allow_zero_bytesused)
+		pr_warn_once("use VIDIOC_DECODER_CMD(V4L2_DEC_CMD_STOP) instead.\n");
+	else
+		pr_warn_once("use the actual size instead.\n");
+}
+
+/**
+ * __fill_vb2_buffer() - fill a vb2_buffer with information provided in a
+ * v4l2_buffer by the userspace. The caller has already verified that struct
+ * v4l2_buffer has a valid number of planes.
+ */
+static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b,
+				struct v4l2_plane *v4l2_planes)
+{
+	unsigned int plane;
+
+	if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
+		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;
+			}
+		}
+		if (b->memory == V4L2_MEMORY_DMABUF) {
+			for (plane = 0; plane < vb->num_planes; ++plane) {
+				v4l2_planes[plane].m.fd =
+					b->m.planes[plane].m.fd;
+				v4l2_planes[plane].length =
+					b->m.planes[plane].length;
+			}
+		}
+
+		/* 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.
+			 *
+			 * If bytesused == 0 for the output buffer, then fall
+			 * back to the full buffer size. In that case
+			 * userspace clearly never bothered to set it and
+			 * it's a safe assumption that they really meant to
+			 * use the full plane sizes.
+			 *
+			 * Some drivers, e.g. old codec drivers, use bytesused == 0
+			 * as a way to indicate that streaming is finished.
+			 * In that case, the driver should use the
+			 * allow_zero_bytesused flag to keep old userspace
+			 * applications working.
+			 */
+			for (plane = 0; plane < vb->num_planes; ++plane) {
+				struct v4l2_plane *pdst = &v4l2_planes[plane];
+				struct v4l2_plane *psrc = &b->m.planes[plane];
+
+				if (psrc->bytesused == 0)
+					vb2_warn_zero_bytesused(vb);
+
+				if (vb->vb2_queue->allow_zero_bytesused)
+					pdst->bytesused = psrc->bytesused;
+				else
+					pdst->bytesused = psrc->bytesused ?
+						psrc->bytesused : pdst->length;
+				pdst->data_offset = psrc->data_offset;
+			}
+		}
+	} 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 bytesused == 0 for the output buffer, then fall back
+		 * to the full buffer size as that's a sensible default.
+		 *
+		 * Some drivers, e.g. old codec drivers, use bytesused == 0 as
+		 * a way to indicate that streaming is finished. In that case,
+		 * the driver should use the allow_zero_bytesused flag to keep
+		 * old userspace applications working.
+		 */
+		if (b->memory == V4L2_MEMORY_USERPTR) {
+			v4l2_planes[0].m.userptr = b->m.userptr;
+			v4l2_planes[0].length = b->length;
+		}
+
+		if (b->memory == V4L2_MEMORY_DMABUF) {
+			v4l2_planes[0].m.fd = b->m.fd;
+			v4l2_planes[0].length = b->length;
+		}
+
+		if (V4L2_TYPE_IS_OUTPUT(b->type)) {
+			if (b->bytesused == 0)
+				vb2_warn_zero_bytesused(vb);
+
+			if (vb->vb2_queue->allow_zero_bytesused)
+				v4l2_planes[0].bytesused = b->bytesused;
+			else
+				v4l2_planes[0].bytesused = b->bytesused ?
+					b->bytesused : v4l2_planes[0].length;
+		} else
+			v4l2_planes[0].bytesused = 0;
+
+	}
+
+	/* Zero flags that the vb2 core handles */
+	vb->v4l2_buf.flags = b->flags & ~V4L2_BUFFER_MASK_FLAGS;
+	if ((vb->vb2_queue->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) !=
+	    V4L2_BUF_FLAG_TIMESTAMP_COPY || !V4L2_TYPE_IS_OUTPUT(b->type)) {
+		/*
+		 * Non-COPY timestamps and non-OUTPUT queues will get
+		 * their timestamp and timestamp source flags from the
+		 * queue.
+		 */
+		vb->v4l2_buf.flags &= ~V4L2_BUF_FLAG_TSTAMP_SRC_MASK;
+	}
+
+	if (V4L2_TYPE_IS_OUTPUT(b->type)) {
+		/*
+		 * For output buffers mask out the timecode flag:
+		 * this will be handled later in vb2_internal_qbuf().
+		 * The 'field' is valid metadata for this output buffer
+		 * and so that needs to be copied here.
+		 */
+		vb->v4l2_buf.flags &= ~V4L2_BUF_FLAG_TIMECODE;
+		vb->v4l2_buf.field = b->field;
+	} else {
+		/* Zero any output buffer flags as this is a capture buffer */
+		vb->v4l2_buf.flags &= ~V4L2_BUFFER_OUT_FLAGS;
+	}
+}
+
+/**
+ * __qbuf_mmap() - handle qbuf of an MMAP buffer
+ */
+static int __qbuf_mmap(struct vb2_buffer *vb, const struct v4l2_buffer *b)
+{
+	__fill_vb2_buffer(vb, b, vb->v4l2_planes);
+	return call_vb_qop(vb, buf_prepare, vb);
+}
+
+/**
+ * __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;
+	enum dma_data_direction dma_dir =
+		V4L2_TYPE_IS_OUTPUT(q->type) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	bool reacquired = vb->planes[0].mem_priv == NULL;
+
+	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
+	/* Copy relevant information provided by the userspace */
+	__fill_vb2_buffer(vb, b, planes);
+
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		/* Skip the plane if already verified */
+		if (vb->v4l2_planes[plane].m.userptr &&
+		    vb->v4l2_planes[plane].m.userptr == planes[plane].m.userptr
+		    && vb->v4l2_planes[plane].length == planes[plane].length)
+			continue;
+
+		dprintk(3, "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]) {
+			dprintk(1, "provided buffer size %u is less than "
+						"setup size %u for plane %d\n",
+						planes[plane].length,
+						q->plane_sizes[plane], plane);
+			ret = -EINVAL;
+			goto err;
+		}
+
+		/* Release previously acquired memory if present */
+		if (vb->planes[plane].mem_priv) {
+			if (!reacquired) {
+				reacquired = true;
+				call_void_vb_qop(vb, buf_cleanup, vb);
+			}
+			call_void_memop(vb, put_userptr, vb->planes[plane].mem_priv);
+		}
+
+		vb->planes[plane].mem_priv = NULL;
+		memset(&vb->v4l2_planes[plane], 0, sizeof(struct v4l2_plane));
+
+		/* Acquire each plane's memory */
+		mem_priv = call_ptr_memop(vb, get_userptr, q->alloc_ctx[plane],
+				      planes[plane].m.userptr,
+				      planes[plane].length, dma_dir);
+		if (IS_ERR_OR_NULL(mem_priv)) {
+			dprintk(1, "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;
+	}
+
+	/*
+	 * 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];
+
+	if (reacquired) {
+		/*
+		 * One or more planes changed, so we must call buf_init to do
+		 * the driver-specific initialization on the newly acquired
+		 * buffer, if provided.
+		 */
+		ret = call_vb_qop(vb, buf_init, vb);
+		if (ret) {
+			dprintk(1, "buffer initialization failed\n");
+			goto err;
+		}
+	}
+
+	ret = call_vb_qop(vb, buf_prepare, vb);
+	if (ret) {
+		dprintk(1, "buffer preparation failed\n");
+		call_void_vb_qop(vb, buf_cleanup, vb);
+		goto err;
+	}
+
+	return 0;
+err:
+	/* In case of errors, release planes that were already acquired */
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		if (vb->planes[plane].mem_priv)
+			call_void_memop(vb, put_userptr, vb->planes[plane].mem_priv);
+		vb->planes[plane].mem_priv = NULL;
+		vb->v4l2_planes[plane].m.userptr = 0;
+		vb->v4l2_planes[plane].length = 0;
+	}
+
+	return ret;
+}
+
+/**
+ * __qbuf_dmabuf() - handle qbuf of a DMABUF buffer
+ */
+static int __qbuf_dmabuf(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;
+	enum dma_data_direction dma_dir =
+		V4L2_TYPE_IS_OUTPUT(q->type) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	bool reacquired = vb->planes[0].mem_priv == NULL;
+
+	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
+	/* Copy relevant information provided by the userspace */
+	__fill_vb2_buffer(vb, b, planes);
+
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		struct dma_buf *dbuf = dma_buf_get(planes[plane].m.fd);
+
+		if (IS_ERR_OR_NULL(dbuf)) {
+			dprintk(1, "invalid dmabuf fd for plane %d\n",
+				plane);
+			ret = -EINVAL;
+			goto err;
+		}
+
+		/* use DMABUF size if length is not provided */
+		if (planes[plane].length == 0)
+			planes[plane].length = dbuf->size;
+
+		if (planes[plane].length < q->plane_sizes[plane]) {
+			dprintk(1, "invalid dmabuf length for plane %d\n",
+				plane);
+			ret = -EINVAL;
+			goto err;
+		}
+
+		/* Skip the plane if already verified */
+		if (dbuf == vb->planes[plane].dbuf &&
+		    vb->v4l2_planes[plane].length == planes[plane].length) {
+			dma_buf_put(dbuf);
+			continue;
+		}
+
+		dprintk(1, "buffer for plane %d changed\n", plane);
+
+		if (!reacquired) {
+			reacquired = true;
+			call_void_vb_qop(vb, buf_cleanup, vb);
+		}
+
+		/* Release previously acquired memory if present */
+		__vb2_plane_dmabuf_put(vb, &vb->planes[plane]);
+		memset(&vb->v4l2_planes[plane], 0, sizeof(struct v4l2_plane));
+
+		/* Acquire each plane's memory */
+		mem_priv = call_ptr_memop(vb, attach_dmabuf, q->alloc_ctx[plane],
+			dbuf, planes[plane].length, dma_dir);
+		if (IS_ERR(mem_priv)) {
+			dprintk(1, "failed to attach dmabuf\n");
+			ret = PTR_ERR(mem_priv);
+			dma_buf_put(dbuf);
+			goto err;
+		}
+
+		vb->planes[plane].dbuf = dbuf;
+		vb->planes[plane].mem_priv = mem_priv;
+	}
+
+	/* TODO: This pins the buffer(s) with  dma_buf_map_attachment()).. but
+	 * really we want to do this just before the DMA, not while queueing
+	 * the buffer(s)..
+	 */
+	for (plane = 0; plane < vb->num_planes; ++plane) {
+		ret = call_memop(vb, map_dmabuf, vb->planes[plane].mem_priv);
+		if (ret) {
+			dprintk(1, "failed to map dmabuf for plane %d\n",
+				plane);
+			goto err;
+		}
+		vb->planes[plane].dbuf_mapped = 1;
+	}
+
+	/*
+	 * Now that everything is in order, copy relevant information
+	 * provided by userspace.
+	 */
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		vb->v4l2_planes[plane] = planes[plane];
+
+	if (reacquired) {
+		/*
+		 * Call driver-specific initialization on the newly acquired buffer,
+		 * if provided.
+		 */
+		ret = call_vb_qop(vb, buf_init, vb);
+		if (ret) {
+			dprintk(1, "buffer initialization failed\n");
+			goto err;
+		}
+	}
+
+	ret = call_vb_qop(vb, buf_prepare, vb);
+	if (ret) {
+		dprintk(1, "buffer preparation failed\n");
+		call_void_vb_qop(vb, buf_cleanup, vb);
+		goto err;
+	}
+
+	return 0;
+err:
+	/* In case of errors, release planes that were already acquired */
+	__vb2_buf_dmabuf_put(vb);
+
+	return ret;
+}
+
+/**
+ * __enqueue_in_driver() - enqueue a vb2_buffer in driver for processing
+ */
+static void __enqueue_in_driver(struct vb2_buffer *vb)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+	unsigned int plane;
+
+	vb->state = VB2_BUF_STATE_ACTIVE;
+	atomic_inc(&q->owned_by_drv_count);
+
+	/* sync buffers */
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		call_void_memop(vb, prepare, vb->planes[plane].mem_priv);
+
+	call_void_vb_qop(vb, buf_queue, vb);
+}
+
+static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+	int ret;
+
+	ret = __verify_length(vb, b);
+	if (ret < 0) {
+		dprintk(1, "plane parameters verification failed: %d\n", ret);
+		return ret;
+	}
+	if (b->field == V4L2_FIELD_ALTERNATE && V4L2_TYPE_IS_OUTPUT(q->type)) {
+		/*
+		 * If the format's field is ALTERNATE, then the buffer's field
+		 * should be either TOP or BOTTOM, not ALTERNATE since that
+		 * makes no sense. The driver has to know whether the
+		 * buffer represents a top or a bottom field in order to
+		 * program any DMA correctly. Using ALTERNATE is wrong, since
+		 * that just says that it is either a top or a bottom field,
+		 * but not which of the two it is.
+		 */
+		dprintk(1, "the field is incorrectly set to ALTERNATE for an output buffer\n");
+		return -EINVAL;
+	}
+
+	if (q->error) {
+		dprintk(1, "fatal error occurred on queue\n");
+		return -EIO;
+	}
+
+	vb->state = VB2_BUF_STATE_PREPARING;
+	vb->v4l2_buf.timestamp.tv_sec = 0;
+	vb->v4l2_buf.timestamp.tv_usec = 0;
+	vb->v4l2_buf.sequence = 0;
+
+	switch (q->memory) {
+	case V4L2_MEMORY_MMAP:
+		ret = __qbuf_mmap(vb, b);
+		break;
+	case V4L2_MEMORY_USERPTR:
+		down_read(&current->mm->mmap_sem);
+		ret = __qbuf_userptr(vb, b);
+		up_read(&current->mm->mmap_sem);
+		break;
+	case V4L2_MEMORY_DMABUF:
+		ret = __qbuf_dmabuf(vb, b);
+		break;
+	default:
+		WARN(1, "Invalid queue type\n");
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		dprintk(1, "buffer preparation failed: %d\n", ret);
+	vb->state = ret ? VB2_BUF_STATE_DEQUEUED : VB2_BUF_STATE_PREPARED;
+
+	return ret;
+}
+
+static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
+				    const char *opname)
+{
+	if (b->type != q->type) {
+		dprintk(1, "%s: invalid buffer type\n", opname);
+		return -EINVAL;
+	}
+
+	if (b->index >= q->num_buffers) {
+		dprintk(1, "%s: buffer index out of range\n", opname);
+		return -EINVAL;
+	}
+
+	if (q->bufs[b->index] == NULL) {
+		/* Should never happen */
+		dprintk(1, "%s: buffer is NULL\n", opname);
+		return -EINVAL;
+	}
+
+	if (b->memory != q->memory) {
+		dprintk(1, "%s: invalid memory type\n", opname);
+		return -EINVAL;
+	}
+
+	return __verify_planes_array(q->bufs[b->index], b);
+}
+
+/**
+ * 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 (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+
+	ret = vb2_queue_or_prepare_buf(q, b, "prepare_buf");
+	if (ret)
+		return ret;
+
+	vb = q->bufs[b->index];
+	if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+		dprintk(1, "invalid buffer state %d\n",
+			vb->state);
+		return -EINVAL;
+	}
+
+	ret = __buf_prepare(vb, b);
+	if (!ret) {
+		/* Fill buffer information for the userspace */
+		__fill_v4l2_buffer(vb, b);
+
+		dprintk(1, "prepare of buffer %d succeeded\n", vb->v4l2_buf.index);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_prepare_buf);
+
+/**
+ * vb2_start_streaming() - Attempt to start streaming.
+ * @q:		videobuf2 queue
+ *
+ * Attempt to start streaming. When this function is called there must be
+ * at least q->min_buffers_needed buffers queued up (i.e. the minimum
+ * number of buffers required for the DMA engine to function). If the
+ * @start_streaming op fails it is supposed to return all the driver-owned
+ * buffers back to vb2 in state QUEUED. Check if that happened and if
+ * not warn and reclaim them forcefully.
+ */
+static int vb2_start_streaming(struct vb2_queue *q)
+{
+	struct vb2_buffer *vb;
+	int ret;
+
+	/*
+	 * If any buffers were queued before streamon,
+	 * we can now pass them to driver for processing.
+	 */
+	list_for_each_entry(vb, &q->queued_list, queued_entry)
+		__enqueue_in_driver(vb);
+
+	/* Tell the driver to start streaming */
+	q->start_streaming_called = 1;
+	ret = call_qop(q, start_streaming, q,
+		       atomic_read(&q->owned_by_drv_count));
+	if (!ret)
+		return 0;
+
+	q->start_streaming_called = 0;
+
+	dprintk(1, "driver refused to start streaming\n");
+	/*
+	 * If you see this warning, then the driver isn't cleaning up properly
+	 * after a failed start_streaming(). See the start_streaming()
+	 * documentation in videobuf2-core.h for more information how buffers
+	 * should be returned to vb2 in start_streaming().
+	 */
+	if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
+		unsigned i;
+
+		/*
+		 * Forcefully reclaim buffers if the driver did not
+		 * correctly return them to vb2.
+		 */
+		for (i = 0; i < q->num_buffers; ++i) {
+			vb = q->bufs[i];
+			if (vb->state == VB2_BUF_STATE_ACTIVE)
+				vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED);
+		}
+		/* Must be zero now */
+		WARN_ON(atomic_read(&q->owned_by_drv_count));
+	}
+	/*
+	 * If done_list is not empty, then start_streaming() didn't call
+	 * vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED) but STATE_ERROR or
+	 * STATE_DONE.
+	 */
+	WARN_ON(!list_empty(&q->done_list));
+	return ret;
+}
+
+static int vb2_internal_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
+{
+	int ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
+	struct vb2_buffer *vb;
+
+	if (ret)
+		return ret;
+
+	vb = q->bufs[b->index];
+
+	switch (vb->state) {
+	case VB2_BUF_STATE_DEQUEUED:
+		ret = __buf_prepare(vb, b);
+		if (ret)
+			return ret;
+		break;
+	case VB2_BUF_STATE_PREPARED:
+		break;
+	case VB2_BUF_STATE_PREPARING:
+		dprintk(1, "buffer still being prepared\n");
+		return -EINVAL;
+	default:
+		dprintk(1, "invalid buffer state %d\n", vb->state);
+		return -EINVAL;
+	}
+
+	/*
+	 * Add to the queued buffers list, a buffer will stay on it until
+	 * dequeued in dqbuf.
+	 */
+	list_add_tail(&vb->queued_entry, &q->queued_list);
+	q->queued_count++;
+	q->waiting_for_buffers = false;
+	vb->state = VB2_BUF_STATE_QUEUED;
+	if (V4L2_TYPE_IS_OUTPUT(q->type)) {
+		/*
+		 * For output buffers copy the timestamp if needed,
+		 * and the timecode field and flag if needed.
+		 */
+		if ((q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) ==
+		    V4L2_BUF_FLAG_TIMESTAMP_COPY)
+			vb->v4l2_buf.timestamp = b->timestamp;
+		vb->v4l2_buf.flags |= b->flags & V4L2_BUF_FLAG_TIMECODE;
+		if (b->flags & V4L2_BUF_FLAG_TIMECODE)
+			vb->v4l2_buf.timecode = b->timecode;
+	}
+
+	/*
+	 * If already streaming, give the buffer to driver for processing.
+	 * If not, the buffer will be given to driver on next streamon.
+	 */
+	if (q->start_streaming_called)
+		__enqueue_in_driver(vb);
+
+	/* Fill buffer information for the userspace */
+	__fill_v4l2_buffer(vb, b);
+
+	/*
+	 * If streamon has been called, and we haven't yet called
+	 * start_streaming() since not enough buffers were queued, and
+	 * we now have reached the minimum number of queued buffers,
+	 * then we can finally call start_streaming().
+	 */
+	if (q->streaming && !q->start_streaming_called &&
+	    q->queued_count >= q->min_buffers_needed) {
+		ret = vb2_start_streaming(q);
+		if (ret)
+			return ret;
+	}
+
+	dprintk(1, "qbuf of buffer %d succeeded\n", vb->v4l2_buf.index);
+	return 0;
+}
+
+/**
+ * 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)
+{
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+
+	return vb2_internal_qbuf(q, b);
+}
+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 (q->error) {
+			dprintk(1, "Queue in error state, will not wait for buffers\n");
+			return -EIO;
+		}
+
+		if (!list_empty(&q->done_list)) {
+			/*
+			 * Found a buffer that we were waiting for.
+			 */
+			break;
+		}
+
+		if (nonblocking) {
+			dprintk(1, "nonblocking and no buffers to dequeue, "
+								"will not wait\n");
+			return -EAGAIN;
+		}
+
+		/*
+		 * We are streaming and blocking, wait for another buffer to
+		 * become ready or for streamoff. Driver's lock is released to
+		 * allow streamoff or qbuf to be called while waiting.
+		 */
+		call_void_qop(q, wait_prepare, q);
+
+		/*
+		 * All locks have been released, it is safe to sleep now.
+		 */
+		dprintk(3, "will sleep waiting for buffers\n");
+		ret = wait_event_interruptible(q->done_wq,
+				!list_empty(&q->done_list) || !q->streaming ||
+				q->error);
+
+		/*
+		 * We need to reevaluate both conditions again after reacquiring
+		 * the locks or return an error if one occurred.
+		 */
+		call_void_qop(q, wait_finish, q);
+		if (ret) {
+			dprintk(1, "sleep was interrupted\n");
+			return ret;
+		}
+	}
+	return 0;
+}
+
+/**
+ * __vb2_get_done_vb() - get a buffer ready for dequeuing
+ *
+ * Will sleep if required for nonblocking == false.
+ */
+static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
+				struct v4l2_buffer *b, int nonblocking)
+{
+	unsigned long flags;
+	int ret;
+
+	/*
+	 * Wait for at least one buffer to become available on the done_list.
+	 */
+	ret = __vb2_wait_for_done_vb(q, nonblocking);
+	if (ret)
+		return ret;
+
+	/*
+	 * Driver's lock has been held since we last verified that done_list
+	 * is not empty, so no need for another list_empty(done_list) check.
+	 */
+	spin_lock_irqsave(&q->done_lock, flags);
+	*vb = list_first_entry(&q->done_list, struct vb2_buffer, done_entry);
+	/*
+	 * Only remove the buffer from done_list if v4l2_buffer can handle all
+	 * the planes.
+	 */
+	ret = __verify_planes_array(*vb, b);
+	if (!ret)
+		list_del(&(*vb)->done_entry);
+	spin_unlock_irqrestore(&q->done_lock, flags);
+
+	return ret;
+}
+
+/**
+ * vb2_wait_for_all_buffers() - wait until all buffers are given back to vb2
+ * @q:		videobuf2 queue
+ *
+ * This function will wait until all buffers that have been given to the driver
+ * by buf_queue() are given back to vb2 with vb2_buffer_done(). It doesn't call
+ * wait_prepare, wait_finish pair. It is intended to be called with all locks
+ * taken, for example from stop_streaming() callback.
+ */
+int vb2_wait_for_all_buffers(struct vb2_queue *q)
+{
+	if (!q->streaming) {
+		dprintk(1, "streaming off, will not wait for buffers\n");
+		return -EINVAL;
+	}
+
+	if (q->start_streaming_called)
+		wait_event(q->done_wq, !atomic_read(&q->owned_by_drv_count));
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_wait_for_all_buffers);
+
+/**
+ * __vb2_dqbuf() - bring back the buffer to the DEQUEUED state
+ */
+static void __vb2_dqbuf(struct vb2_buffer *vb)
+{
+	struct vb2_queue *q = vb->vb2_queue;
+	unsigned int i;
+
+	/* nothing to do if the buffer is already dequeued */
+	if (vb->state == VB2_BUF_STATE_DEQUEUED)
+		return;
+
+	vb->state = VB2_BUF_STATE_DEQUEUED;
+
+	/* unmap DMABUF buffer */
+	if (q->memory == V4L2_MEMORY_DMABUF)
+		for (i = 0; i < vb->num_planes; ++i) {
+			if (!vb->planes[i].dbuf_mapped)
+				continue;
+			call_void_memop(vb, unmap_dmabuf, vb->planes[i].mem_priv);
+			vb->planes[i].dbuf_mapped = 0;
+		}
+}
+
+static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
+{
+	struct vb2_buffer *vb = NULL;
+	int ret;
+
+	if (b->type != q->type) {
+		dprintk(1, "invalid buffer type\n");
+		return -EINVAL;
+	}
+	ret = __vb2_get_done_vb(q, &vb, b, nonblocking);
+	if (ret < 0)
+		return ret;
+
+	switch (vb->state) {
+	case VB2_BUF_STATE_DONE:
+		dprintk(3, "returning done buffer\n");
+		break;
+	case VB2_BUF_STATE_ERROR:
+		dprintk(3, "returning done buffer with errors\n");
+		break;
+	default:
+		dprintk(1, "invalid buffer state\n");
+		return -EINVAL;
+	}
+
+	call_void_vb_qop(vb, buf_finish, vb);
+
+	/* Fill buffer information for the userspace */
+	__fill_v4l2_buffer(vb, b);
+	/* Remove from videobuf queue */
+	list_del(&vb->queued_entry);
+	q->queued_count--;
+	/* go back to dequeued state */
+	__vb2_dqbuf(vb);
+
+	dprintk(1, "dqbuf of buffer %d, with state %d\n",
+			vb->v4l2_buf.index, vb->state);
+
+	return 0;
+}
+
+/**
+ * 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)
+{
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+	return vb2_internal_dqbuf(q, b, nonblocking);
+}
+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->start_streaming_called)
+		call_void_qop(q, stop_streaming, q);
+
+	/*
+	 * If you see this warning, then the driver isn't cleaning up properly
+	 * in stop_streaming(). See the stop_streaming() documentation in
+	 * videobuf2-core.h for more information how buffers should be returned
+	 * to vb2 in stop_streaming().
+	 */
+	if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
+		for (i = 0; i < q->num_buffers; ++i)
+			if (q->bufs[i]->state == VB2_BUF_STATE_ACTIVE)
+				vb2_buffer_done(q->bufs[i], VB2_BUF_STATE_ERROR);
+		/* Must be zero now */
+		WARN_ON(atomic_read(&q->owned_by_drv_count));
+	}
+
+	q->streaming = 0;
+	q->start_streaming_called = 0;
+	q->queued_count = 0;
+	q->error = 0;
+
+	/*
+	 * Remove all buffers from videobuf's list...
+	 */
+	INIT_LIST_HEAD(&q->queued_list);
+	/*
+	 * ...and done list; userspace will not receive any buffers it
+	 * has not already dequeued before initiating cancel.
+	 */
+	INIT_LIST_HEAD(&q->done_list);
+	atomic_set(&q->owned_by_drv_count, 0);
+	wake_up_all(&q->done_wq);
+
+	/*
+	 * Reinitialize all buffers for next use.
+	 * Make sure to call buf_finish for any queued buffers. Normally
+	 * that's done in dqbuf, but that's not going to happen when we
+	 * cancel the whole queue. Note: this code belongs here, not in
+	 * __vb2_dqbuf() since in vb2_internal_dqbuf() there is a critical
+	 * call to __fill_v4l2_buffer() after buf_finish(). That order can't
+	 * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
+	 */
+	for (i = 0; i < q->num_buffers; ++i) {
+		struct vb2_buffer *vb = q->bufs[i];
+
+		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+			vb->state = VB2_BUF_STATE_PREPARED;
+			call_void_vb_qop(vb, buf_finish, vb);
+		}
+		__vb2_dqbuf(vb);
+	}
+}
+
+static int vb2_internal_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
+{
+	int ret;
+
+	if (type != q->type) {
+		dprintk(1, "invalid stream type\n");
+		return -EINVAL;
+	}
+
+	if (q->streaming) {
+		dprintk(3, "already streaming\n");
+		return 0;
+	}
+
+	if (!q->num_buffers) {
+		dprintk(1, "no buffers have been allocated\n");
+		return -EINVAL;
+	}
+
+	if (q->num_buffers < q->min_buffers_needed) {
+		dprintk(1, "need at least %u allocated buffers\n",
+				q->min_buffers_needed);
+		return -EINVAL;
+	}
+
+	/*
+	 * Tell driver to start streaming provided sufficient buffers
+	 * are available.
+	 */
+	if (q->queued_count >= q->min_buffers_needed) {
+		ret = vb2_start_streaming(q);
+		if (ret) {
+			__vb2_queue_cancel(q);
+			return ret;
+		}
+	}
+
+	q->streaming = 1;
+
+	dprintk(3, "successful\n");
+	return 0;
+}
+
+/**
+ * vb2_queue_error() - signal a fatal error on the queue
+ * @q:		videobuf2 queue
+ *
+ * Flag that a fatal unrecoverable error has occurred and wake up all processes
+ * waiting on the queue. Polling will now set POLLERR and queuing and dequeuing
+ * buffers will return -EIO.
+ *
+ * The error flag will be cleared when cancelling the queue, either from
+ * vb2_streamoff or vb2_queue_release. Drivers should thus not call this
+ * function before starting the stream, otherwise the error flag will remain set
+ * until the queue is released when closing the device node.
+ */
+void vb2_queue_error(struct vb2_queue *q)
+{
+	q->error = 1;
+
+	wake_up_all(&q->done_wq);
+}
+EXPORT_SYMBOL_GPL(vb2_queue_error);
+
+/**
+ * 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)
+{
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+	return vb2_internal_streamon(q, type);
+}
+EXPORT_SYMBOL_GPL(vb2_streamon);
+
+static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
+{
+	if (type != q->type) {
+		dprintk(1, "invalid stream type\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Cancel will pause streaming and remove all buffers from the driver
+	 * and videobuf, effectively returning control over them to userspace.
+	 *
+	 * Note that we do this even if q->streaming == 0: if you prepare or
+	 * queue buffers, and then call streamoff without ever having called
+	 * streamon, you would still expect those buffers to be returned to
+	 * their normal dequeued state.
+	 */
+	__vb2_queue_cancel(q);
+	q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
+
+	dprintk(3, "successful\n");
+	return 0;
+}
+
+/**
+ * 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 (vb2_fileio_is_active(q)) {
+		dprintk(1, "file io in progress\n");
+		return -EBUSY;
+	}
+	return vb2_internal_streamoff(q, type);
+}
+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_expbuf() - Export a buffer as a file descriptor
+ * @q:		videobuf2 queue
+ * @eb:		export buffer structure passed from userspace to vidioc_expbuf
+ *		handler in driver
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_expbuf handler in driver.
+ */
+int vb2_expbuf(struct vb2_queue *q, struct v4l2_exportbuffer *eb)
+{
+	struct vb2_buffer *vb = NULL;
+	struct vb2_plane *vb_plane;
+	int ret;
+	struct dma_buf *dbuf;
+
+	if (q->memory != V4L2_MEMORY_MMAP) {
+		dprintk(1, "queue is not currently set up for mmap\n");
+		return -EINVAL;
+	}
+
+	if (!q->mem_ops->get_dmabuf) {
+		dprintk(1, "queue does not support DMA buffer exporting\n");
+		return -EINVAL;
+	}
+
+	if (eb->flags & ~(O_CLOEXEC | O_ACCMODE)) {
+		dprintk(1, "queue does support only O_CLOEXEC and access mode flags\n");
+		return -EINVAL;
+	}
+
+	if (eb->type != q->type) {
+		dprintk(1, "invalid buffer type\n");
+		return -EINVAL;
+	}
+
+	if (eb->index >= q->num_buffers) {
+		dprintk(1, "buffer index out of range\n");
+		return -EINVAL;
+	}
+
+	vb = q->bufs[eb->index];
+
+	if (eb->plane >= vb->num_planes) {
+		dprintk(1, "buffer plane out of range\n");
+		return -EINVAL;
+	}
+
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "expbuf: file io in progress\n");
+		return -EBUSY;
+	}
+
+	vb_plane = &vb->planes[eb->plane];
+
+	dbuf = call_ptr_memop(vb, get_dmabuf, vb_plane->mem_priv, eb->flags & O_ACCMODE);
+	if (IS_ERR_OR_NULL(dbuf)) {
+		dprintk(1, "failed to export buffer %d, plane %d\n",
+			eb->index, eb->plane);
+		return -EINVAL;
+	}
+
+	ret = dma_buf_fd(dbuf, eb->flags & ~O_ACCMODE);
+	if (ret < 0) {
+		dprintk(3, "buffer %d, plane %d failed to export (%d)\n",
+			eb->index, eb->plane, ret);
+		dma_buf_put(dbuf);
+		return ret;
+	}
+
+	dprintk(3, "buffer %d, plane %d exported as %d descriptor\n",
+		eb->index, eb->plane, ret);
+	eb->fd = ret;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_expbuf);
+
+/**
+ * vb2_mmap() - map video buffers into application address space
+ * @q:		videobuf2 queue
+ * @vma:	vma passed to the mmap file operation handler in the driver
+ *
+ * Should be called from mmap file operation handler of a driver.
+ * This function maps one plane of one of the available video buffers to
+ * userspace. To map whole video memory allocated on reqbufs, this function
+ * has to be called once per each plane per each buffer previously allocated.
+ *
+ * When the userspace application calls mmap, it passes to it an offset returned
+ * to it earlier by the means of vidioc_querybuf handler. That offset acts as
+ * a "cookie", which is then used to identify the plane to be mapped.
+ * This function finds a plane with a matching offset and a mapping is performed
+ * by the means of a provided memory operation.
+ *
+ * The return values from this function are intended to be directly returned
+ * from the mmap handler in driver.
+ */
+int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
+{
+	unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
+	struct vb2_buffer *vb;
+	unsigned int buffer = 0, plane = 0;
+	int ret;
+	unsigned long length;
+
+	if (q->memory != 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;
+		}
+	}
+	if (vb2_fileio_is_active(q)) {
+		dprintk(1, "mmap: file io in progress\n");
+		return -EBUSY;
+	}
+
+	/*
+	 * Find the plane corresponding to the offset passed by userspace.
+	 */
+	ret = __find_plane_by_offset(q, off, &buffer, &plane);
+	if (ret)
+		return ret;
+
+	vb = q->bufs[buffer];
+
+	/*
+	 * MMAP requires page_aligned buffers.
+	 * The buffer length was page_aligned at __vb2_buf_mem_alloc(),
+	 * so, we need to do the same here.
+	 */
+	length = PAGE_ALIGN(vb->v4l2_planes[plane].length);
+	if (length < (vma->vm_end - vma->vm_start)) {
+		dprintk(1,
+			"MMAP invalid, as it would overflow buffer length\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&q->mmap_lock);
+	ret = call_memop(vb, mmap, vb->planes[plane].mem_priv, vma);
+	mutex_unlock(&q->mmap_lock);
+	if (ret)
+		return ret;
+
+	dprintk(3, "buffer %d, plane %d successfully mapped\n", buffer, plane);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_mmap);
+
+#ifndef CONFIG_MMU
+unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
+				    unsigned long addr,
+				    unsigned long len,
+				    unsigned long pgoff,
+				    unsigned long flags)
+{
+	unsigned long off = pgoff << PAGE_SHIFT;
+	struct vb2_buffer *vb;
+	unsigned int buffer, plane;
+	void *vaddr;
+	int ret;
+
+	if (q->memory != 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];
+
+	vaddr = vb2_plane_vaddr(vb, plane);
+	return vaddr ? (unsigned long)vaddr : -EINVAL;
+}
+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);
+	}
+
+	if (!V4L2_TYPE_IS_OUTPUT(q->type) && !(req_events & (POLLIN | POLLRDNORM)))
+		return res;
+	if (V4L2_TYPE_IS_OUTPUT(q->type) && !(req_events & (POLLOUT | POLLWRNORM)))
+		return res;
+
+	/*
+	 * Start file I/O emulator only if streaming API has not been used yet.
+	 */
+	if (q->num_buffers == 0 && !vb2_fileio_is_active(q)) {
+		if (!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 the queue isn't streaming, or if the
+	 * error flag is set.
+	 */
+	if (!vb2_is_streaming(q) || q->error)
+		return res | POLLERR;
+	/*
+	 * For compatibility with vb1: if QBUF hasn't been called yet, then
+	 * return POLLERR as well. This only affects capture queues, output
+	 * queues will always initialize waiting_for_buffers to false.
+	 */
+	if (q->waiting_for_buffers)
+		return res | POLLERR;
+
+	/*
+	 * For output streams you can write as long as there are fewer buffers
+	 * queued than there are buffers available.
+	 */
+	if (V4L2_TYPE_IS_OUTPUT(q->type) && q->queued_count < q->num_buffers)
+		return res | POLLOUT | POLLWRNORM;
+
+	if (list_empty(&q->done_list))
+		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)
+{
+	/*
+	 * Sanity check
+	 */
+	if (WARN_ON(!q)			  ||
+	    WARN_ON(!q->ops)		  ||
+	    WARN_ON(!q->mem_ops)	  ||
+	    WARN_ON(!q->type)		  ||
+	    WARN_ON(!q->io_modes)	  ||
+	    WARN_ON(!q->ops->queue_setup) ||
+	    WARN_ON(!q->ops->buf_queue)   ||
+	    WARN_ON(q->timestamp_flags &
+		    ~(V4L2_BUF_FLAG_TIMESTAMP_MASK |
+		      V4L2_BUF_FLAG_TSTAMP_SRC_MASK)))
+		return -EINVAL;
+
+	/* Warn that the driver should choose an appropriate timestamp type */
+	WARN_ON((q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) ==
+		V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN);
+
+	INIT_LIST_HEAD(&q->queued_list);
+	INIT_LIST_HEAD(&q->done_list);
+	spin_lock_init(&q->done_lock);
+	mutex_init(&q->mmap_lock);
+	init_waitqueue_head(&q->done_wq);
+
+	if (q->buf_struct_size == 0)
+		q->buf_struct_size = sizeof(struct vb2_buffer);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_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);
+	mutex_lock(&q->mmap_lock);
+	__vb2_queue_free(q, q->num_buffers);
+	mutex_unlock(&q->mmap_lock);
+}
+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
+ *
+ * @cur_index:	the index of the buffer currently being read from or
+ *		written to. If equal to q->num_buffers then a new buffer
+ *		must be dequeued.
+ * @initial_index: in the read() case all buffers are queued up immediately
+ *		in __vb2_init_fileio() and __vb2_perform_fileio() just cycles
+ *		buffers. However, in the write() case no buffers are initially
+ *		queued, instead whenever a buffer is full it is queued up by
+ *		__vb2_perform_fileio(). Only once all available buffers have
+ *		been queued up will __vb2_perform_fileio() start to dequeue
+ *		buffers. This means that initially __vb2_perform_fileio()
+ *		needs to know what buffer index to use when it is queuing up
+ *		the buffers for the first time. That initial index is stored
+ *		in this field. Once it is equal to q->num_buffers all
+ *		available buffers have been queued and __vb2_perform_fileio()
+ *		should start the normal dequeue/queue cycle.
+ *
+ * vb2 provides a compatibility layer and emulator of file io (read and
+ * write) calls on top of streaming API. For proper operation it required
+ * this structure to save the driver state between each call of the read
+ * or write function.
+ */
+struct vb2_fileio_data {
+	struct v4l2_requestbuffers req;
+	struct v4l2_plane p;
+	struct v4l2_buffer b;
+	struct vb2_fileio_buf bufs[VIDEO_MAX_FRAME];
+	unsigned int cur_index;
+	unsigned int initial_index;
+	unsigned int q_count;
+	unsigned int dq_count;
+	unsigned read_once:1;
+	unsigned write_immediately:1;
+};
+
+/**
+ * __vb2_init_fileio() - initialize file io emulator
+ * @q:		videobuf2 queue
+ * @read:	mode selector (1 means read, 0 means write)
+ */
+static int __vb2_init_fileio(struct vb2_queue *q, int read)
+{
+	struct vb2_fileio_data *fileio;
+	int i, ret;
+	unsigned int count = 0;
+
+	/*
+	 * Sanity check
+	 */
+	if (WARN_ON((read && !(q->io_modes & VB2_READ)) ||
+		    (!read && !(q->io_modes & VB2_WRITE))))
+		return -EINVAL;
+
+	/*
+	 * Check if device supports mapping buffers to kernel virtual space.
+	 */
+	if (!q->mem_ops->vaddr)
+		return -EBUSY;
+
+	/*
+	 * Check if streaming api has not been already activated.
+	 */
+	if (q->streaming || q->num_buffers > 0)
+		return -EBUSY;
+
+	/*
+	 * Start with count 1, driver can increase it in queue_setup()
+	 */
+	count = 1;
+
+	dprintk(3, "setting up file io: mode %s, count %d, read_once %d, write_immediately %d\n",
+		(read) ? "read" : "write", count, q->fileio_read_once,
+		q->fileio_write_immediately);
+
+	fileio = kzalloc(sizeof(struct vb2_fileio_data), GFP_KERNEL);
+	if (fileio == NULL)
+		return -ENOMEM;
+
+	fileio->read_once = q->fileio_read_once;
+	fileio->write_immediately = q->fileio_write_immediately;
+
+	/*
+	 * Request buffers and use MMAP type to force driver
+	 * to allocate buffers by itself.
+	 */
+	fileio->req.count = count;
+	fileio->req.memory = V4L2_MEMORY_MMAP;
+	fileio->req.type = q->type;
+	q->fileio = fileio;
+	ret = __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) {
+			ret = -EINVAL;
+			goto err_reqbufs;
+		}
+		fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
+	}
+
+	/*
+	 * Read mode requires pre queuing of all buffers.
+	 */
+	if (read) {
+		bool is_multiplanar = V4L2_TYPE_IS_MULTIPLANAR(q->type);
+
+		/*
+		 * 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;
+			if (is_multiplanar) {
+				memset(&fileio->p, 0, sizeof(fileio->p));
+				b->m.planes = &fileio->p;
+				b->length = 1;
+			}
+			b->memory = q->memory;
+			b->index = i;
+			ret = vb2_internal_qbuf(q, b);
+			if (ret)
+				goto err_reqbufs;
+			fileio->bufs[i].queued = 1;
+		}
+		/*
+		 * All buffers have been queued, so mark that by setting
+		 * initial_index to q->num_buffers
+		 */
+		fileio->initial_index = q->num_buffers;
+		fileio->cur_index = q->num_buffers;
+	}
+
+	/*
+	 * Start streaming.
+	 */
+	ret = vb2_internal_streamon(q, q->type);
+	if (ret)
+		goto err_reqbufs;
+
+	return ret;
+
+err_reqbufs:
+	fileio->req.count = 0;
+	__reqbufs(q, &fileio->req);
+
+err_kfree:
+	q->fileio = NULL;
+	kfree(fileio);
+	return ret;
+}
+
+/**
+ * __vb2_cleanup_fileio() - free resourced used by file io emulator
+ * @q:		videobuf2 queue
+ */
+static int __vb2_cleanup_fileio(struct vb2_queue *q)
+{
+	struct vb2_fileio_data *fileio = q->fileio;
+
+	if (fileio) {
+		vb2_internal_streamoff(q, q->type);
+		q->fileio = NULL;
+		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;
+	bool is_multiplanar = V4L2_TYPE_IS_MULTIPLANAR(q->type);
+	/*
+	 * When using write() to write data to an output video node the vb2 core
+	 * should set timestamps if V4L2_BUF_FLAG_TIMESTAMP_COPY is set. Nobody
+	 * else is able to provide this information with the write() operation.
+	 */
+	bool set_timestamp = !read &&
+		(q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) ==
+		V4L2_BUF_FLAG_TIMESTAMP_COPY;
+	int ret, index;
+
+	dprintk(3, "mode %s, offset %ld, count %zd, %sblocking\n",
+		read ? "read" : "write", (long)*ppos, count,
+		nonblock ? "non" : "");
+
+	if (!data)
+		return -EINVAL;
+
+	/*
+	 * Initialize emulator on first call.
+	 */
+	if (!vb2_fileio_is_active(q)) {
+		ret = __vb2_init_fileio(q, read);
+		dprintk(3, "vb2_init_fileio result: %d\n", ret);
+		if (ret)
+			return ret;
+	}
+	fileio = q->fileio;
+
+	/*
+	 * Check if we need to dequeue the buffer.
+	 */
+	index = fileio->cur_index;
+	if (index >= q->num_buffers) {
+		/*
+		 * Call vb2_dqbuf to get buffer back.
+		 */
+		memset(&fileio->b, 0, sizeof(fileio->b));
+		fileio->b.type = q->type;
+		fileio->b.memory = q->memory;
+		if (is_multiplanar) {
+			memset(&fileio->p, 0, sizeof(fileio->p));
+			fileio->b.m.planes = &fileio->p;
+			fileio->b.length = 1;
+		}
+		ret = vb2_internal_dqbuf(q, &fileio->b, nonblock);
+		dprintk(5, "vb2_dqbuf result: %d\n", ret);
+		if (ret)
+			return ret;
+		fileio->dq_count += 1;
+
+		fileio->cur_index = index = fileio->b.index;
+		buf = &fileio->bufs[index];
+
+		/*
+		 * Get number of bytes filled by the driver
+		 */
+		buf->pos = 0;
+		buf->queued = 0;
+		buf->size = read ? vb2_get_plane_payload(q->bufs[index], 0)
+				 : vb2_plane_size(q->bufs[index], 0);
+		/* Compensate for data_offset on read in the multiplanar case. */
+		if (is_multiplanar && read &&
+		    fileio->b.m.planes[0].data_offset < buf->size) {
+			buf->pos = fileio->b.m.planes[0].data_offset;
+			buf->size -= buf->pos;
+		}
+	} else {
+		buf = &fileio->bufs[index];
+	}
+
+	/*
+	 * Limit count on last few bytes of the buffer.
+	 */
+	if (buf->pos + count > buf->size) {
+		count = buf->size - buf->pos;
+		dprintk(5, "reducing read count: %zd\n", count);
+	}
+
+	/*
+	 * Transfer data to userspace.
+	 */
+	dprintk(3, "copying %zd bytes - buffer %d, offset %u\n",
+		count, index, buf->pos);
+	if (read)
+		ret = copy_to_user(data, buf->vaddr + buf->pos, count);
+	else
+		ret = copy_from_user(buf->vaddr + buf->pos, data, count);
+	if (ret) {
+		dprintk(3, "error copying data\n");
+		return -EFAULT;
+	}
+
+	/*
+	 * Update counters.
+	 */
+	buf->pos += count;
+	*ppos += count;
+
+	/*
+	 * Queue next buffer if required.
+	 */
+	if (buf->pos == buf->size || (!read && fileio->write_immediately)) {
+		/*
+		 * Check if this is the last buffer to read.
+		 */
+		if (read && fileio->read_once && fileio->dq_count == 1) {
+			dprintk(3, "read limit reached\n");
+			return __vb2_cleanup_fileio(q);
+		}
+
+		/*
+		 * Call vb2_qbuf and give buffer to the driver.
+		 */
+		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;
+		if (is_multiplanar) {
+			memset(&fileio->p, 0, sizeof(fileio->p));
+			fileio->p.bytesused = buf->pos;
+			fileio->b.m.planes = &fileio->p;
+			fileio->b.length = 1;
+		}
+		if (set_timestamp)
+			v4l2_get_timestamp(&fileio->b.timestamp);
+		ret = vb2_internal_qbuf(q, &fileio->b);
+		dprintk(5, "vb2_dbuf result: %d\n", ret);
+		if (ret)
+			return ret;
+
+		/*
+		 * Buffer has been queued, update the status
+		 */
+		buf->pos = 0;
+		buf->queued = 1;
+		buf->size = vb2_plane_size(q->bufs[index], 0);
+		fileio->q_count += 1;
+		/*
+		 * If we are queuing up buffers for the first time, then
+		 * increase initial_index by one.
+		 */
+		if (fileio->initial_index < q->num_buffers)
+			fileio->initial_index++;
+		/*
+		 * The next buffer to use is either a buffer that's going to be
+		 * queued for the first time (initial_index < q->num_buffers)
+		 * or it is equal to q->num_buffers, meaning that the next
+		 * time we need to dequeue a buffer since we've now queued up
+		 * all the 'first time' buffers.
+		 */
+		fileio->cur_index = fileio->initial_index;
+	}
+
+	/*
+	 * Return proper number of bytes processed.
+	 */
+	if (ret == 0)
+		ret = count;
+	return ret;
+}
+
+size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
+		loff_t *ppos, int nonblocking)
+{
+	return __vb2_perform_fileio(q, data, count, ppos, nonblocking, 1);
+}
+EXPORT_SYMBOL_GPL(vb2_read);
+
+size_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
+		loff_t *ppos, int nonblocking)
+{
+	return __vb2_perform_fileio(q, (char __user *) data, count,
+							ppos, nonblocking, 0);
+}
+EXPORT_SYMBOL_GPL(vb2_write);
+
+struct vb2_threadio_data {
+	struct task_struct *thread;
+	vb2_thread_fnc fnc;
+	void *priv;
+	bool stop;
+};
+
+static int vb2_thread(void *data)
+{
+	struct vb2_queue *q = data;
+	struct vb2_threadio_data *threadio = q->threadio;
+	struct vb2_fileio_data *fileio = q->fileio;
+	bool set_timestamp = false;
+	int prequeue = 0;
+	int index = 0;
+	int ret = 0;
+
+	if (V4L2_TYPE_IS_OUTPUT(q->type)) {
+		prequeue = q->num_buffers;
+		set_timestamp =
+			(q->timestamp_flags & V4L2_BUF_FLAG_TIMESTAMP_MASK) ==
+			V4L2_BUF_FLAG_TIMESTAMP_COPY;
+	}
+
+	set_freezable();
+
+	for (;;) {
+		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;
+		if (prequeue) {
+			fileio->b.index = index++;
+			prequeue--;
+		} else {
+			call_void_qop(q, wait_finish, q);
+			if (!threadio->stop)
+				ret = vb2_internal_dqbuf(q, &fileio->b, 0);
+			call_void_qop(q, wait_prepare, q);
+			dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
+		}
+		if (ret || threadio->stop)
+			break;
+		try_to_freeze();
+
+		vb = q->bufs[fileio->b.index];
+		if (!(fileio->b.flags & V4L2_BUF_FLAG_ERROR))
+			if (threadio->fnc(vb, threadio->priv))
+				break;
+		call_void_qop(q, wait_finish, q);
+		if (set_timestamp)
+			v4l2_get_timestamp(&fileio->b.timestamp);
+		if (!threadio->stop)
+			ret = vb2_internal_qbuf(q, &fileio->b);
+		call_void_qop(q, wait_prepare, q);
+		if (ret || threadio->stop)
+			break;
+	}
+
+	/* Hmm, linux becomes *very* unhappy without this ... */
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule();
+	}
+	return 0;
+}
+
+/*
+ * This function should not be used for anything else but the videobuf2-dvb
+ * support. If you think you have another good use-case for this, then please
+ * contact the linux-media mailinglist first.
+ */
+int vb2_thread_start(struct vb2_queue *q, vb2_thread_fnc fnc, void *priv,
+		     const char *thread_name)
+{
+	struct vb2_threadio_data *threadio;
+	int ret = 0;
+
+	if (q->threadio)
+		return -EBUSY;
+	if (vb2_is_busy(q))
+		return -EBUSY;
+	if (WARN_ON(q->fileio))
+		return -EBUSY;
+
+	threadio = kzalloc(sizeof(*threadio), GFP_KERNEL);
+	if (threadio == NULL)
+		return -ENOMEM;
+	threadio->fnc = fnc;
+	threadio->priv = priv;
+
+	ret = __vb2_init_fileio(q, !V4L2_TYPE_IS_OUTPUT(q->type));
+	dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
+	if (ret)
+		goto nomem;
+	q->threadio = threadio;
+	threadio->thread = kthread_run(vb2_thread, q, "vb2-%s", thread_name);
+	if (IS_ERR(threadio->thread)) {
+		ret = PTR_ERR(threadio->thread);
+		threadio->thread = NULL;
+		goto nothread;
+	}
+	return 0;
+
+nothread:
+	__vb2_cleanup_fileio(q);
+nomem:
+	kfree(threadio);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_thread_start);
+
+int vb2_thread_stop(struct vb2_queue *q)
+{
+	struct vb2_threadio_data *threadio = q->threadio;
+	int err;
+
+	if (threadio == NULL)
+		return 0;
+	threadio->stop = true;
+	/* Wake up all pending sleeps in the thread */
+	vb2_queue_error(q);
+	err = kthread_stop(threadio->thread);
+	__vb2_cleanup_fileio(q);
+	threadio->thread = NULL;
+	kfree(threadio);
+	q->threadio = NULL;
+	return err;
+}
+EXPORT_SYMBOL_GPL(vb2_thread_stop);
+
+/*
+ * 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);
+
+int vb2_ioctl_expbuf(struct file *file, void *priv, struct v4l2_exportbuffer *p)
+{
+	struct video_device *vdev = video_devdata(file);
+
+	if (vb2_queue_is_busy(vdev, file))
+		return -EBUSY;
+	return vb2_expbuf(vdev->queue, p);
+}
+EXPORT_SYMBOL_GPL(vb2_ioctl_expbuf);
+
+/* 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 mutex *lock)
+{
+	struct video_device *vdev = video_devdata(file);
+
+	if (lock)
+		mutex_lock(lock);
+	if (file->private_data == vdev->queue->owner) {
+		vb2_queue_release(vdev->queue);
+		vdev->queue->owner = NULL;
+	}
+	if (lock)
+		mutex_unlock(lock);
+	return v4l2_fh_release(file);
+}
+EXPORT_SYMBOL_GPL(_vb2_fop_release);
+
+int vb2_fop_release(struct file *file)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
+
+	return _vb2_fop_release(file, lock);
+}
+EXPORT_SYMBOL_GPL(vb2_fop_release);
+
+ssize_t vb2_fop_write(struct file *file, const char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
+	int err = -EBUSY;
+
+	if (!(vdev->queue->io_modes & VB2_WRITE))
+		return -EINVAL;
+	if (lock && mutex_lock_interruptible(lock))
+		return -ERESTARTSYS;
+	if (vb2_queue_is_busy(vdev, file))
+		goto exit;
+	err = vb2_write(vdev->queue, buf, count, ppos,
+		       file->f_flags & O_NONBLOCK);
+	if (vdev->queue->fileio)
+		vdev->queue->owner = file->private_data;
+exit:
+	if (lock)
+		mutex_unlock(lock);
+	return err;
+}
+EXPORT_SYMBOL_GPL(vb2_fop_write);
+
+ssize_t vb2_fop_read(struct file *file, char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
+	int err = -EBUSY;
+
+	if (!(vdev->queue->io_modes & VB2_READ))
+		return -EINVAL;
+	if (lock && mutex_lock_interruptible(lock))
+		return -ERESTARTSYS;
+	if (vb2_queue_is_busy(vdev, file))
+		goto exit;
+	err = vb2_read(vdev->queue, buf, count, ppos,
+		       file->f_flags & O_NONBLOCK);
+	if (vdev->queue->fileio)
+		vdev->queue->owner = file->private_data;
+exit:
+	if (lock)
+		mutex_unlock(lock);
+	return err;
+}
+EXPORT_SYMBOL_GPL(vb2_fop_read);
+
+unsigned int vb2_fop_poll(struct file *file, poll_table *wait)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct vb2_queue *q = vdev->queue;
+	struct mutex *lock = q->lock ? q->lock : vdev->lock;
+	unsigned res;
+	void *fileio;
+
+	/*
+	 * If this helper doesn't know how to lock, then you shouldn't be using
+	 * it but you should write your own.
+	 */
+	WARN_ON(!lock);
+
+	if (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 (!fileio && q->fileio)
+		q->owner = file->private_data;
+	if (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");