On Wed, Sep 02, 2020 at 10:56:46AM +0100, Kieran Bingham wrote:
> Hi Kaaira, Dafna,
>
> On 28/08/2020 21:37, Dafna Hirschfeld wrote:
> > 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
>
> Which entity is this? Is it the start, or the end of the pipeline? I.e.
> the sensor? or the capture ?
It is the capture, I will add it to the documentation..thanks
>
> >>>> + *
> >>>> + * 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
>
> Matching on entity names is a bit awkward, as they could be changed I
> guess quite easily, and easily missed in this string matching.
Agreed, I need to think of a better way to prevent this
>
> I haven't fully understood this code block yet to work out if there's
> another way we could do this though, but reading ahead I see there might
> be a way to 'walk the graph' on a per-stream basis which might be a good
> way of factoring this path.
>
> Although there still needs to be a construction of the paths available
> to a stream which splits from the sensor.
>
>
> >>
> >>>
> >>> 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.
>
> If this doesn't end up refactored with other helpers, then indeed a few
> comments might help the readabilty here. The distinctions of each
> re-initialisation of the graph walk are hard to interpret the purpose.
>
>
>
> >
> > 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.
>
> Being able to use a direct helper to walk the pipeline cleanly sounds
> promising indeed.
>
> I suspect at some point int he next patches though - I'm going to see
> something that needs to have full visibility of all paths enabled from
> the sensor, as I think I recall that the thread will then process all
> (enabled) entities in a single pass.
Yes, that exactly is the problem :( This helper (that dafna has shared)
can walk through one path, while the thread (which processes the frames)
needs to view all the entites in all connected paths
> --
> Kieran
>
>
> >
> > 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;
> >>>>
>
> --
> Regards
> --
> Kieran
