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@xxxxxxxxxxxxx>
---
drivers/media/common/videobuf2/videobuf2-core.c | 10 ++++++++--
include/media/videobuf2-core.h | 13 +++++++++++++
2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 41a832dd1426..a183edf11586 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -865,7 +865,7 @@ 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));
/*
@@ -917,7 +917,7 @@ 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;
/*
@@ -2521,6 +2521,12 @@ int vb2_core_queue_init(struct vb2_queue *q)
if (WARN_ON(q->supports_requests && q->min_queued_buffers))
return -EINVAL;
+ q->min_reqbufs_allocation = max_t(unsigned int,
+ 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);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 56719a26a46c..7b84b4e2e273 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -553,6 +553,18 @@ struct vb2_buf_ops {
* VIDIOC_REQBUFS will ensure at least @min_queued_buffers
* 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. Drivers can set this if there has to
+ * be a certain number of buffers available for the hardware to
+ * work effectively. If set, then @min_reqbufs_allocation must be
+ * larger than @min_queued_buffers + 1.
+ * This field is only used by VIDIOC_REQBUFS. This allows calling
+ * that ioctl with a buffer count of 1 and it will be automatically
+ * adjusted to a workable buffer count. VIDIOC_CREATE_BUFS will not
+ * modify the requested buffer count.
+ * If this field is > 3, then it is highly recommended that the
+ * driver implements the V4L2_CID_MIN_BUFFERS_FOR_CAPTURE/OUTPUT
+ * control.
*/
/*
* Private elements (won't appear at the uAPI book):
@@ -618,6 +630,7 @@ 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];
--
2.40.1
