Hi,

On Mon, 2018-06-25 at 15:32 +0200, Maxime Ripard wrote:

On Thu, Jun 21, 2018 at 05:38:23PM +0200, Paul Kocialkowski wrote:

quoted

Hi,

On Wed, 2018-06-13 at 16:07 +0200, Maxime Ripard wrote:

quoted

Some codec needs to perform some additional task when a decoding is started
and stopped, and not only at every frame.

For example, the H264 decoding support needs to allocate buffers that will
be used in the decoding process, but do not need to change over time, or at
each frame.

In order to allow that for codecs, introduce a start and stop hook that
will be called if present at start_streaming and stop_streaming time.

Signed-off-by: Maxime Ripard <redacted>
---
 .../platform/sunxi/cedrus/sunxi_cedrus_common.h    |  2 ++
 .../platform/sunxi/cedrus/sunxi_cedrus_video.c     | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h
index a2a507eb9fc9..20c78ec1f037 100644
--- a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h
+++ b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h

@@ -120,6 +120,8 @@ struct sunxi_cedrus_dec_ops {
 	enum sunxi_cedrus_irq_status (*irq_status)(struct sunxi_cedrus_ctx *ctx);
 	void (*setup)(struct sunxi_cedrus_ctx *ctx,
 		      struct sunxi_cedrus_run *run);
+	int (*start)(struct sunxi_cedrus_ctx *ctx);
+	void (*stop)(struct sunxi_cedrus_ctx *ctx);
 	void (*trigger)(struct sunxi_cedrus_ctx *ctx);
 };
 

diff --git a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_video.c b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_video.c
index fb7b081a5bb7..d93461178857 100644
--- a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_video.c
+++ b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_video.c

@@ -416,6 +416,8 @@ static int sunxi_cedrus_buf_prepare(struct vb2_buffer *vb)
 static int sunxi_cedrus_start_streaming(struct vb2_queue *q, unsigned int count)
 {
 	struct sunxi_cedrus_ctx *ctx = vb2_get_drv_priv(q);
+	struct sunxi_cedrus_dev *dev = ctx->dev;
+	int ret = 0;
 
 	switch (ctx->vpu_src_fmt->fourcc) {
 	case V4L2_PIX_FMT_MPEG2_FRAME:

@@ -425,16 +427,26 @@ static int sunxi_cedrus_start_streaming(struct vb2_queue *q, unsigned int count)
 		return -EINVAL;
 	}
 
-	return 0;
+	if (V4L2_TYPE_IS_OUTPUT(q->type) &&

I suppose this check was put in place to ensure that ->start is only
called once, but what if start_streaming is called multiple times on
output? Am I totally unsure about whether the API guarantees that we
only get one start_streaming call per buffer queue, regardless of how
many userspace issues.

If we don't have such a guarantee, we probably need an internal
mechanism to avoid having ->start called more than once.

As far as I understand it, start_streaming can only be called once:
https://elixir.bootlin.com/linux/latest/source/include/media/videobuf2-core.h#L357

And there's definitely a check in vb2_core_streamon:

	if (q->streaming) {
		dprintk(3, "already streaming\n");
		return 0;
	}

so it looks like we're safe :)

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com
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