Commit 6662edcd authored by Benjamin Gaignard's avatar Benjamin Gaignard Committed by Hans Verkuil
Browse files

media: videobuf2: Add min_reqbufs_allocation field to vb2_queue structure 



Add 'min_reqbufs_allocation' field in the vb2_queue structure so drivers
can specify the minimum number of buffers to allocate when calling
VIDIOC_REQBUFS.
When initializing the queue, v4l2 core makes sure that the following
constraints are respected:
- the minimum number of buffers to allocate must be at least 2 because
one buffer is used by the hardware while the other is being processed
by userspace.
-if the driver needs 'min_queued_buffers' in the queue before calling
start_streaming(), then the minimum requirement is 'min_queued_buffers + 1'
to keep at least one buffer available for userspace.

Simplify __vb2_init_fileio() by using 'min_reqbufs_allocation' directly
to avoid duplicating the minimum number of buffers to allocate computation.

Signed-off-by: default avatarBenjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
parent d7cdb594

drivers/media/common/videobuf2/videobuf2-core.c

+23 −15
Original line number Diff line number Diff line
@@ -866,7 +866,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory, 
	/*

	 * Make sure the requested values and current defaults are sane.

	 */

	num_buffers = max_t(unsigned int, *count, q->min_queued_buffers);

	num_buffers = max_t(unsigned int, *count, q->min_reqbufs_allocation);

	num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);

	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));

	/*
@@ -918,7 +918,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory, 
	 * 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_queued_buffers)

	if (allocated_buffers < q->min_reqbufs_allocation)

		ret = -ENOMEM;



	/*
@@ -2524,6 +2524,25 @@ int vb2_core_queue_init(struct vb2_queue *q) 
	if (WARN_ON(q->supports_requests && q->min_queued_buffers))

		return -EINVAL;



	/*

	 * The minimum requirement is 2: one buffer is used

	 * by the hardware while the other is being processed by userspace.

	 */

	if (q->min_reqbufs_allocation < 2)

		q->min_reqbufs_allocation = 2;



	/*

	 * If the driver needs 'min_queued_buffers' in the queue before

	 * calling start_streaming() then the minimum requirement is

	 * 'min_queued_buffers + 1' to keep at least one buffer available

	 * for userspace.

	 */

	if (q->min_reqbufs_allocation < q->min_queued_buffers + 1)

		q->min_reqbufs_allocation = q->min_queued_buffers + 1;



	if (WARN_ON(q->min_reqbufs_allocation > q->max_num_buffers))

		return -EINVAL;



	INIT_LIST_HEAD(&q->queued_list);

	INIT_LIST_HEAD(&q->done_list);

	spin_lock_init(&q->done_lock);
@@ -2717,7 +2736,6 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) 
	struct vb2_fileio_data *fileio;

	struct vb2_buffer *vb;

	int i, ret;

	unsigned int count = 0;



	/*

	 * Sanity check
@@ -2738,18 +2756,8 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) 
	if (q->streaming || vb2_get_num_buffers(q) > 0)

		return -EBUSY;



	/*

	 * Start with q->min_queued_buffers + 1, driver can increase it in

	 * queue_setup()

	 *

	 * 'min_queued_buffers' buffers need to be queued up before you

	 * can start streaming, plus 1 for userspace (or in this case,

	 * kernelspace) processing.

	 */

	count = max(2, q->min_queued_buffers + 1);



	dprintk(q, 3, "setting up file io: mode %s, count %d, read_once %d, write_immediately %d\n",

		(read) ? "read" : "write", count, q->fileio_read_once,

		(read) ? "read" : "write", q->min_reqbufs_allocation, q->fileio_read_once,

		q->fileio_write_immediately);



	fileio = kzalloc(sizeof(*fileio), GFP_KERNEL);
@@ -2763,7 +2771,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) 
	 * Request buffers and use MMAP type to force driver

	 * to allocate buffers by itself.

	 */

	fileio->count = count;

	fileio->count = q->min_reqbufs_allocation;

	fileio->memory = VB2_MEMORY_MMAP;

	fileio->type = q->type;

	q->fileio = fileio;

include/media/videobuf2-core.h

+14 −1
Original line number Diff line number Diff line
@@ -549,9 +549,21 @@ struct vb2_buf_ops { 
 *		@start_streaming can be called. Used when a DMA engine

 *		cannot be started unless at least this number of buffers

 *		have been queued into the driver.

 *		VIDIOC_REQBUFS will ensure at least @min_queued_buffers

 *		VIDIOC_REQBUFS will ensure at least @min_queued_buffers + 1

 *		buffers will be allocated. Note that VIDIOC_CREATE_BUFS will not

 *		modify the requested buffer count.

 * @min_reqbufs_allocation: the minimum number of buffers to be allocated when

 *		calling VIDIOC_REQBUFS. Note that VIDIOC_CREATE_BUFS will *not*

 *		modify the requested buffer count and does not use this field.

 *		Drivers can set this if there has to be a certain number of

 *		buffers available for the hardware to work effectively.

 *		This allows calling VIDIOC_REQBUFS with a buffer count of 1 and

 *		it will be automatically adjusted to a workable	buffer count.

 *		If set, then @min_reqbufs_allocation must be larger than

 *		@min_queued_buffers + 1.

 *		If this field is > 3, then it is highly recommended that the

 *		driver implements the V4L2_CID_MIN_BUFFERS_FOR_CAPTURE/OUTPUT

 *		control.

 * @alloc_devs:	&struct device memory type/allocator-specific per-plane device

 */

/*
@@ -622,6 +634,7 @@ struct vb2_queue { 
	u32				timestamp_flags;

	gfp_t				gfp_flags;

	u32				min_queued_buffers;

	u32				min_reqbufs_allocation;



	struct device			*alloc_devs[VB2_MAX_PLANES];