[PATCH v3 2/2] videobuf2: Add min_reqbufs_allocation field to vb2_queue structure

[Benjamin Gaignard <benjamin.gaignard@collabora.com>]

Add 'min_reqbufs_allocation' field in vb2_queue structure so drivers
can specificy the minimum number of buffers to allocate when calling
VIDIOC_REQBUFS.
If used this minimum should be higher than the minimum number of
queued buffers needed to start streaming.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
---
 drivers/media/common/videobuf2/videobuf2-core.c | 1 +
 include/media/videobuf2-core.h                  | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 7b6d89641e66..3bc30d107308 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -866,6 +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, num_buffers, 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));
 	/*
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 6d11cb724e95..252d34cc47d3 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -550,6 +550,11 @@ 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.
+ * @min_reqbufs_allocation: the minimum number of buffers allocated when
+ *		calling VIDIOC_REQBUFS. Used when drivers need a to
+ *		specify a minimum buffers allocation before setup a queue.
+ *		If min_queued_buffers < min_queued_buffers then min_queued_buffers
+ *		is the minimum.
  */
 /*
  * Private elements (won't appear at the uAPI book):
@@ -615,6 +620,7 @@ 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];
 
-- 
2.39.2