linux/drivers/media/test-drivers/vimc/vimc-streamer.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * vimc-streamer.c Virtual Media Controller Driver
 *
 * Copyright (C) 2018 Lucas A. M. Magalhães <[email protected]>
 *
 */

#include <linux/init.h>
#include <linux/freezer.h>
#include <linux/kthread.h>

#include "vimc-streamer.h"

/**
 * vimc_get_source_entity - get the entity connected with the first sink pad
 *
 * @ent:	reference media_entity
 *
 * 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.
 */
static struct media_entity *vimc_get_source_entity(struct media_entity *ent)
{ … }

/**
 * vimc_streamer_pipeline_terminate - Disable stream in all ved in stream
 *
 * @stream: the pointer to the stream structure with the pipeline to be
 *	    disabled.
 *
 * Calls s_stream to disable the stream in each entity of the pipeline
 *
 */
static void vimc_streamer_pipeline_terminate(struct vimc_stream *stream)
{ … }

/**
 * vimc_streamer_pipeline_init - Initializes the stream structure
 *
 * @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.
 *
 * Return: 0 if success, error code otherwise.
 */
static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
				       struct vimc_ent_device *ved)
{ … }

/**
 * vimc_streamer_thread - Process frames through the pipeline
 *
 * @data:	vimc_stream struct of the current stream
 *
 * 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).
 */
static int vimc_streamer_thread(void *data)
{ … }

/**
 * vimc_streamer_s_stream - Start/stop the streaming on the media pipeline
 *
 * @stream:	the pointer to the stream structure of the current stream
 * @ved:	pointer to the vimc entity of the entity of the stream
 * @enable:	flag to determine if stream should start/stop
 *
 * 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.
 */
int vimc_streamer_s_stream(struct vimc_stream *stream,
			   struct vimc_ent_device *ved,
			   int enable)
{ … }