8.1.13. The Virtual Media Controller Driver (vimc)¶
8.1.13.1. Source code documentation¶
8.1.13.1.1. vimc-streamer¶
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struct
vimc_stream¶ struct that represents a stream in the pipeline
Definition
struct vimc_stream {
struct media_pipeline pipe;
struct vimc_ent_device *ved_pipeline[VIMC_STREAMER_PIPELINE_MAX_SIZE];
unsigned int pipe_size;
struct task_struct *kthread;
};
Members
pipe- the media pipeline object associated with this stream
ved_pipeline- array containing all the entities participating in the stream. The order is from a video device (usually a capture device) where stream_on was called, to the entity generating the first base image to be processed in the pipeline.
pipe_size- size of ved_pipeline
kthread- thread that generates the frames of the stream.
Description
When the user call stream_on in a video device, struct vimc_stream is
used to keep track of all entities and subdevices that generates and
process frames for the stream.
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struct media_entity *
vimc_get_source_entity(struct media_entity *ent)¶ get the entity connected with the first sink pad
Parameters
struct media_entity *ent- reference media_entity
Description
Helper function that returns the media entity containing the source pad linked with the first sink pad from the given media entity pad list.
Return
The source pad or NULL, if it wasn’t found.
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void
vimc_streamer_pipeline_terminate(struct vimc_stream *stream)¶ Disable stream in all ved in stream
Parameters
struct vimc_stream *stream- the pointer to the stream structure with the pipeline to be disabled.
Description
Calls s_stream to disable the stream in each entity of the pipeline
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int
vimc_streamer_pipeline_init(struct vimc_stream *stream, struct vimc_ent_device *ved)¶ Initializes the stream structure
Parameters
struct vimc_stream *stream- the pointer to the stream structure to be initialized
struct vimc_ent_device *ved- the pointer to the vimc entity initializing the stream
Description
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.
Return
0 if success, error code otherwise.
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int
vimc_streamer_thread(void *data)¶ Process frames through the pipeline
Parameters
void *data- vimc_stream struct of the current stream
Description
From the source to the sink, gets a frame from each subdevice and send to the next one of the pipeline at a fixed framerate.
Return
Always zero (created as int instead of void to comply with
kthread API).
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int
vimc_streamer_s_stream(struct vimc_stream *stream, struct vimc_ent_device *ved, int enable)¶ Start/stop the streaming on the media pipeline
Parameters
struct vimc_stream *stream- the pointer to the stream structure of the current stream
struct vimc_ent_device *ved- pointer to the vimc entity of the entity of the stream
int enable- flag to determine if stream should start/stop
Description
When starting, check if there is no stream->kthread allocated. This
should indicate that a stream is already running. Then, it initializes the
pipeline, creates and runs a kthread to consume buffers through the pipeline.
When stopping, analogously check if there is a stream running, stop the
thread and terminates the pipeline.
Return
0 if success, error code otherwise.