[RFC PATCH 3/5] media: iris: Signal V4L2_EVENT_EOS only at the end of a drain

[Christian Cortner <ccortner@gmail.com>]

iris_vb2_buffer_done() and iris_vb2_buf_queue() queue V4L2_EVENT_EOS and
mark the m2m context as stopped for every capture buffer flagged
V4L2_BUF_FLAG_LAST, including the one that ends a dynamic resolution
change. In the stateful decoder interface the (deprecated) EOS event is
part of the drain sequence only, and a resolution change is not the end
of the stream: a client that still acts on the event, like ffmpeg's
h264_v4l2m2m decoder, stops decoding at the first resolution change in
the stream. And since nothing in the driver clears the stopped mark
again, the EOS event of the drain at the real end of such a stream is
never sent.

Queue the event, and mark the context as stopped, only when the LAST
buffer ends a drain, that is when IRIS_INST_SUB_DRAIN_LAST is set. Both
HFI generations set it before they return the LAST buffer of a drain,
for the decoder and the encoder alike.

Fixes: 84e17adae3e3 ("media: iris: add support for dynamic resolution change")
Cc: stable@vger.kernel.org
Assisted-by: LLM sparse smatch
---
Reference only, not for merging (no Signed-off-by); see the cover
letter.

 drivers/media/platform/qcom/iris/iris_buffer.c | 7 ++++++-
 drivers/media/platform/qcom/iris/iris_vb2.c    | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_buffer.c b/drivers/media/platform/qcom/iris/iris_buffer.c
index eb8de60c1177..ff2a1b331ac2 100644
--- a/drivers/media/platform/qcom/iris/iris_buffer.c
+++ b/drivers/media/platform/qcom/iris/iris_buffer.c
@@ -913,7 +913,12 @@ int iris_vb2_buffer_done(struct iris_inst *inst, struct iris_buffer *buf)
 	}
 
 	if (vbuf->flags & V4L2_BUF_FLAG_LAST) {
-		if (!v4l2_m2m_has_stopped(m2m_ctx)) {
+		/*
+		 * Only a drain ends with V4L2_EVENT_EOS: the LAST buffer of a
+		 * source change is not the end of the stream.
+		 */
+		if (inst->sub_state & IRIS_INST_SUB_DRAIN_LAST &&
+		    !v4l2_m2m_has_stopped(m2m_ctx)) {
 			const struct v4l2_event ev = { .type = V4L2_EVENT_EOS };
 
 			v4l2_event_queue_fh(&inst->fh, &ev);
diff --git a/drivers/media/platform/qcom/iris/iris_vb2.c b/drivers/media/platform/qcom/iris/iris_vb2.c
index 8faf709c26c1..b820b3e43910 100644
--- a/drivers/media/platform/qcom/iris/iris_vb2.c
+++ b/drivers/media/platform/qcom/iris/iris_vb2.c
@@ -324,7 +324,9 @@ void iris_vb2_buf_queue(struct vb2_buffer *vb2)
 			vbuf->field = V4L2_FIELD_NONE;
 			vb2_set_plane_payload(vb2, 0, 0);
 			v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_DONE);
-			if (!v4l2_m2m_has_stopped(m2m_ctx)) {
+			/* EOS ends a drain only, see iris_vb2_buffer_done() */
+			if (inst->sub_state & IRIS_INST_SUB_DRAIN_LAST &&
+			    !v4l2_m2m_has_stopped(m2m_ctx)) {
 				v4l2_event_queue_fh(&inst->fh, &eos);
 				v4l2_m2m_mark_stopped(m2m_ctx);
 			}
-- 
2.56.0