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Subject[RFC v5 10/11] [media] vb2: add out-fence support to QBUF
Date
From: Gustavo Padovan <gustavo.padovan@collabora.com>

If V4L2_BUF_FLAG_OUT_FENCE flag is present on the QBUF call we create
an out_fence and send its fd to userspace on the fence_fd field as a
return arg for the QBUF call.

The fence is signaled on buffer_done(), when the job on the buffer is
finished.

With out-fences we do not allow drivers to requeue buffers through vb2,
instead we flag an error on the buffer, signals it fence with error and
return it to userspace.

v6
- get rid of the V4L2_EVENT_OUT_FENCE event. We always keep the
ordering in vb2 for queueing in the driver, so the event is not
necessary anymore and the out_fence_fd is sent back to userspace
on QBUF call return arg
- do not allow requeueing with out-fences, instead mark the buffer
with an error and wake up to userspace.
- send the out_fence_fd back to userspace on the fence_fd field

v5:
- delay fd_install to DQ_EVENT (Hans)
- if queue is fully ordered send OUT_FENCE event right away
(Brian)
- rename 'q->ordered' to 'q->ordered_in_driver'
- merge change to implement OUT_FENCE event here

v4:
- return the out_fence_fd in the BUF_QUEUED event(Hans)

v3: - add WARN_ON_ONCE(q->ordered) on requeueing (Hans)
- set the OUT_FENCE flag if there is a fence pending (Hans)
- call fd_install() after vb2_core_qbuf() (Hans)
- clean up fence if vb2_core_qbuf() fails (Hans)
- add list to store sync_file and fence for the next queued buffer

v2: check if the queue is ordered.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
---
drivers/media/v4l2-core/videobuf2-core.c | 42 +++++++++++++++++++++++++++++---
drivers/media/v4l2-core/videobuf2-v4l2.c | 21 +++++++++++++++-
2 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 8b4f0e9bcb36..2eb5ffa8e028 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -354,6 +354,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
vb->planes[plane].length = plane_sizes[plane];
vb->planes[plane].min_length = plane_sizes[plane];
}
+ vb->out_fence_fd = -1;
q->bufs[vb->index] = vb;

/* Allocate video buffer memory for the MMAP type */
@@ -934,10 +935,26 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
case VB2_BUF_STATE_QUEUED:
return;
case VB2_BUF_STATE_REQUEUEING:
- if (q->start_streaming_called)
- __enqueue_in_driver(vb);
- return;
+
+ if (!vb->out_fence) {
+ if (q->start_streaming_called)
+ __enqueue_in_driver(vb);
+ return;
+ }
+
+ /* Do not allow requeuing with explicit synchronization,
+ * report it as an error to userspace */
+ state = VB2_BUF_STATE_ERROR;
+
+ /* fall through */
default:
+ if (state == VB2_BUF_STATE_ERROR)
+ dma_fence_set_error(vb->out_fence, -EFAULT);
+ dma_fence_signal(vb->out_fence);
+ dma_fence_put(vb->out_fence);
+ vb->out_fence = NULL;
+ vb->out_fence_fd = -1;
+
/* Inform any processes that may be waiting for buffers */
wake_up(&q->done_wq);
break;
@@ -1325,12 +1342,18 @@ EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index)
{
struct vb2_buffer *vb;
+ u64 context;

vb = q->bufs[index];

vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);

- vb->out_fence = vb2_fence_alloc(q->out_fence_context);
+ if (q->ordered_in_driver)
+ context = q->out_fence_context;
+ else
+ context = dma_fence_context_alloc(1);
+
+ vb->out_fence = vb2_fence_alloc(context);
if (!vb->out_fence) {
put_unused_fd(vb->out_fence_fd);
return -ENOMEM;
@@ -1594,6 +1617,9 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
if (pb)
call_void_bufop(q, fill_user_buffer, vb, pb);

+ fd_install(vb->out_fence_fd, vb->sync_file->file);
+ vb->sync_file = NULL;
+
dprintk(2, "qbuf of buffer %d succeeded\n", vb->index);
return 0;

@@ -1860,6 +1886,12 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
}

/*
+ * Renew out-fence context.
+ */
+ if (q->ordered_in_driver)
+ q->out_fence_context = dma_fence_context_alloc(1);
+
+ /*
* Remove all buffers from videobuf's list...
*/
INIT_LIST_HEAD(&q->queued_list);
@@ -2191,6 +2223,8 @@ int vb2_core_queue_init(struct vb2_queue *q)
spin_lock_init(&q->done_lock);
mutex_init(&q->mmap_lock);
init_waitqueue_head(&q->done_wq);
+ if (q->ordered_in_driver)
+ q->out_fence_context = dma_fence_context_alloc(1);

if (q->buf_struct_size == 0)
q->buf_struct_size = sizeof(struct vb2_buffer);
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 4c09ea007d90..f2e60d2908ae 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -212,7 +212,13 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
b->sequence = vbuf->sequence;
b->reserved = 0;

- b->fence_fd = -1;
+ if (vb->out_fence) {
+ b->flags |= V4L2_BUF_FLAG_OUT_FENCE;
+ b->fence_fd = vb->out_fence_fd;
+ } else {
+ b->fence_fd = -1;
+ }
+
if (vb->in_fence)
b->flags |= V4L2_BUF_FLAG_IN_FENCE;
else
@@ -489,6 +495,10 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
ret = __verify_planes_array(vb, b);
if (!ret)
vb2_core_querybuf(q, b->index, b);
+
+ /* Do not return the out-fence fd on querybuf */
+ if (vb->out_fence)
+ b->fence_fd = -1;
return ret;
}
EXPORT_SYMBOL(vb2_querybuf);
@@ -593,6 +603,15 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
}
}

+ if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+ ret = vb2_setup_out_fence(q, b->index);
+ if (ret) {
+ dprintk(1, "failed to set up out-fence\n");
+ dma_fence_put(fence);
+ return ret;
+ }
+ }
+
return vb2_core_qbuf(q, b->index, b, fence);
}
EXPORT_SYMBOL_GPL(vb2_qbuf);
--
2.13.6
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