On 07/07/2017 04:00 AM, Gustavo Padovan wrote:
2017-07-06 Hans Verkuil <hverkuil@xxxxxxxxx>:
On 06/16/17 09:39, Gustavo Padovan wrote:
From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
Receive in-fence from userspace and add support for waiting on them
before queueing the buffer to the driver. Buffers are only queued
to the driver once they are ready. A buffer is ready when its
in-fence signals.
v2:
- fix vb2_queue_or_prepare_buf() ret check
- remove check for VB2_MEMORY_DMABUF only (Javier)
- check num of ready buffers to start streaming
- when queueing, start from the first ready buffer
- handle queue cancel
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
drivers/media/Kconfig | 1 +
drivers/media/v4l2-core/videobuf2-core.c | 97 +++++++++++++++++++++++++-------
drivers/media/v4l2-core/videobuf2-v4l2.c | 15 ++++-
include/media/videobuf2-core.h | 7 ++-
4 files changed, 99 insertions(+), 21 deletions(-)
<snip>
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 110fb45..e6ad77f 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -23,6 +23,7 @@
#include <linux/sched.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
+#include <linux/sync_file.h>
#include <media/v4l2-dev.h>
#include <media/v4l2-fh.h>
@@ -560,6 +561,7 @@ EXPORT_SYMBOL_GPL(vb2_create_bufs);
int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
{
+ struct dma_fence *fence = NULL;
int ret;
if (vb2_fileio_is_active(q)) {
@@ -568,7 +570,18 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
}
ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
- return ret ? ret : vb2_core_qbuf(q, b->index, b);
+ if (ret)
+ return ret;
+
+ if (b->flags & V4L2_BUF_FLAG_IN_FENCE) {
+ fence = sync_file_get_fence(b->fence_fd);
+ if (!fence) {
+ dprintk(1, "failed to get in-fence from fd\n");
+ return -EINVAL;
+ }
+ }
+
+ return ret ? ret : vb2_core_qbuf(q, b->index, b, fence);
}
EXPORT_SYMBOL_GPL(vb2_qbuf);
You need to adapt __fill_v4l2_buffer so it sets the IN_FENCE buffer flag
if there is a fence pending. It should also fill in fence_fd.
It was userspace who sent the fence_fd in the first place. Why do we
need to send it back? The initial plan was - from a userspace point of view
- to send the in-fence in the fence_fd field and receive the out-fence
in the same field.
As per setting the IN_FENCE flag, that is racy, as the fence can signal
just after we called __fill_v4l2_buffer. Why is it important to set it?
Because when running VIDIOC_QUERYBUF it should return the current state of
the buffer, including whether it has a fence. You can do something like
v4l2-ctl --list-buffers to see how many buffers are queued up and the state
of each buffer. Can be useful to e.g. figure out why a video capture seems
to stall. Knowing that all queued buffers are all waiting for a fence is
very useful information. Whether the fence_fd should also be set here or
only in dqbuf is something I don't know (not enough knowledge about how
fences are supposed to work). The IN/OUT_FENCE flags should definitely be
reported though.
Anyway, remember that this callback is called from various vb2 ioctls:
qbuf, dqbuf, querybuf and prepare_buf.
Querybuf especially can be called at any time.
Regards,
Hans
