Re: [PATCH v3 4/9] media: vimc: Separate starting stream from pipeline initialisation
From: Dafna Hirschfeld
Date: Fri Aug 28 2020 - 16:37:23 EST
Hi,
Am 21.08.20 um 23:01 schrieb Kaaira Gupta:
Hi,
On Fri, Aug 21, 2020 at 05:11:23PM +0200, Dafna Hirschfeld wrote:
Am 19.08.20 um 20:04 schrieb Kaaira Gupta:
Separate the process of initialising pipeline array from starting
streaming for all entities in path of a stream. This is needed because
multiple streams can stream, but only one pipeline object is needed.
Process frames only for those entities in a pipeline which are
streaming. This is known through their use counts.
Signed-off-by: Kaaira Gupta <kgupta@xxxxxxxxxxxxx>
---
.../media/test-drivers/vimc/vimc-streamer.c | 95 ++++++++++++++++---
1 file changed, 83 insertions(+), 12 deletions(-)
diff --git a/drivers/media/test-drivers/vimc/vimc-streamer.c b/drivers/media/test-drivers/vimc/vimc-streamer.c
index c1644d69686d..cc40ecabe95a 100644
--- a/drivers/media/test-drivers/vimc/vimc-streamer.c
+++ b/drivers/media/test-drivers/vimc/vimc-streamer.c
@@ -40,33 +40,30 @@ static void vimc_streamer_pipeline_terminate(struct vimc_stream *stream)
}
/**
- * vimc_streamer_pipeline_init - Initializes the stream structure
+ * vimc_streamer_stream_start - Starts streaming for all entities
+ * in a stream
*
- * @stream: the pointer to the stream structure to be initialized
* @ved: the pointer to the vimc entity initializing the stream
*
- * Initializes the stream structure. Walks through the entity graph to
- * construct the pipeline used later on the streamer thread.
- * Calls vimc_streamer_s_stream() to enable stream in all entities of
- * the pipeline.
+ * Walks through the entity graph to call vimc_streamer_s_stream()
+ * to enable stream in all entities in path of a stream.
*
* Return: 0 if success, error code otherwise.
*/
-static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
- struct vimc_ent_device *ved)
+static int vimc_streamer_stream_start(struct vimc_stream *stream,
+ struct vimc_ent_device *ved)
{
struct media_entity *entity;
struct video_device *vdev;
struct v4l2_subdev *sd;
+ int stream_size = 0;
int ret = 0;
- stream->pipe_size = 0;
- while (stream->pipe_size < VIMC_STREAMER_PIPELINE_MAX_SIZE) {
+ while (stream_size < VIMC_STREAMER_PIPELINE_MAX_SIZE) {
if (!ved) {
vimc_streamer_pipeline_terminate(stream);
return -EINVAL;
}
- stream->ved_pipeline[stream->pipe_size++] = ved;
if (is_media_entity_v4l2_subdev(ved->ent)) {
sd = media_entity_to_v4l2_subdev(ved->ent);
@@ -104,6 +101,73 @@ static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
entity);
ved = video_get_drvdata(vdev);
}
+ stream_size++;
+ }
+
+ vimc_streamer_pipeline_terminate(stream);
+ return -EINVAL;
+}
+
+/**
+ * vimc_streamer_pipeline_init - Initialises pipeline and pipe size
+ *
+ * @stream: the pointer to the stream structure
+ * @ved: the pointer to the vimc entity initializing the stream pipeline
+ *
+ * Walks through the entity graph to initialise ved_pipeline and updates
+ * pipe_size too.
+ *
+ * Return: 0 if success, error code otherwise.
+ */
+static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
+ struct vimc_ent_device *ved)
+{
+ struct media_entity *entity;
+ struct media_device *mdev;
+ struct media_graph graph;
+ struct video_device *vdev;
+ struct v4l2_subdev *sd;
+ int ret;
+
+ entity = ved->ent;
+ mdev = entity->graph_obj.mdev;
+
+ ret = media_graph_walk_init(&graph, mdev);
+ if (ret)
+ return ret;
+
+ media_graph_walk_start(&graph, entity);
+
+ /*
+ * Start pipeline array initialisation from RAW Capture only to get
+ * entities in the correct order of their frame processing.
+ */
+ if (!strncmp(entity->name, "RGB", 3)) {
I don't understand this condition, way is it good for?
I have explained that later in the reply
I think the function should be generic and not assume names of entities
or specific topology.
It doesn't assume the topology, rather it is in place just to make sure
that the entities in ved_pipeline are in correct order.
+ entity = media_graph_walk_next(&graph);
+ mdev = entity->graph_obj.mdev;
+ media_graph_walk_cleanup(&graph);
+
+ ret = media_graph_walk_init(&graph, mdev);
+ if (ret)
+ return ret;
+ media_graph_walk_start(&graph, entity);
Hi, can you explain what this code does?
Why does it start the search in the next entity?
+ }
+
+ while (stream->pipe_size < VIMC_STREAMER_PIPELINE_MAX_SIZE) {
+ if (is_media_entity_v4l2_subdev(entity)) {
+ sd = media_entity_to_v4l2_subdev(entity);
+ ved = v4l2_get_subdevdata(sd);
+ } else {
+ vdev = container_of(entity, struct video_device, entity);
+ ved = video_get_drvdata(vdev);
+ }
+ stream->ved_pipeline[stream->pipe_size++] = ved;
+ entity = media_graph_walk_next(&graph);
+
+ if (!strcmp(entity->name, stream->ved_pipeline[0]->ent->name)) {
I also don't understand this condition
+ media_graph_walk_cleanup(&graph);
+ return 0;
+ }
}
It is not clear what this function does, it looks like it adds to 'ved_pipeline'
all entities that are connected to the video node, in addition to the entities
that where there from previous calls, so some entities appear several times.
This function returns all the entities in a pipe, weather they are
streaming or not. For example, if only the RAW Capture 1 streams, or
RGB/YUB capture streams, or both stream..in all three cases ved_pipeline
will have the same entities, in exactly same order, and all will occur just once.
Since media_graph_walk goes to each node of the graph, it returns back
to the first one (as its a graph), hence the last condition, ie,
if (!strcmp(entity->name, stream->ved_pipeline[0]->ent->name)) {
makes sure that the first entity is not added again to the array.
First condition, ie
if (!strncmp(entity->name, "RGB", 3)) {
Just makes sure that the search starts at RGB capture only. This is
because, in case of any other video node, the order of entities, as you
have mentioned later in the mail, will not be desirable, ie it won't
start at sensor and end at captures. So this condition just takes care
that all the entities in ved_pipeline array are in correct order
(starting at sensor, ending at captures).
It is better to compare to the whole name of the entity to make it more clear.
Also I think it is better to document that this function is called only upon the
first streaming node.
I still think this function should be independent of the topology.
Maybe you can use Helen's patch that allow walking a graph only opposite to the link direction: https://patchwork.kernel.org/patch/11564899/
This ensures that the Sensor will be first in the graph walk. Then the streaming thread
iterates the ved_pipeline from 0 upwards and not from 'pipe_size' downwards.
Thanks,
Dafna
Thanks,
Kaaira
I think there is no need to use the graph walk here but to access the source entity
in each iteration, the way done in vimc_streamer_stream_start
also.
I think the code should iterate here until it reaches an entity that is already streaming,
this means that the entity is already in the `ved_pipeline`, also you should make sure
that the sensor is the first entity that process a frame, therefore the sensor should be
at the end/start of the list of entities. Generally each entity should appear exactly once
in the 'ved_pipeline' array and the entities should be ordered such that when calling 'process_frame'
on one entity should be after calling 'process_frame' on its source entity.
maybe it is easyer to implement if 'ved_pipeline' is a linked list.
Thanks,
Dafna
vimc_streamer_pipeline_terminate(stream);
@@ -138,8 +202,11 @@ static int vimc_streamer_thread(void *data)
for (i = stream->pipe_size - 1; i >= 0; i--) {
ved = stream->ved_pipeline[i];
- ret = ved->process_frame(ved);
+ if (atomic_read(&ved->use_count) == 0)
+ continue;
+
+ ret = ved->process_frame(ved);
if (ret)
break;
}
@@ -179,6 +246,10 @@ int vimc_streamer_s_stream(struct vimc_stream *stream,
if (stream->kthread)
return 0;
+ ret = vimc_streamer_stream_start(stream, ved);
+ if (ret)
+ return ret;
+
ret = vimc_streamer_pipeline_init(stream, ved);
if (ret)
return ret;