// SPDX-License-Identifier: GPL-2.0+
/*
 * vimc-streamer.c Virtual Media Controller Driver
 *
 * Copyright (C) 2018 Lucas A. M. Magalhães <lucmaga@gmail.com>
 *
 */

#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)
{
        struct media_pad *pad;
        int i;

        for (i = 0; i < ent->num_pads; i++) {
                if (ent->pads[i].flags & MEDIA_PAD_FL_SOURCE)
                        continue;
                pad = media_pad_remote_pad_first(&ent->pads[i]);
                return pad ? pad->entity : NULL;
        }
        return NULL;
}

/**
 * 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)
{
        struct vimc_ent_device *ved;
        struct v4l2_subdev *sd;

        while (stream->pipe_size) {
                stream->pipe_size--;
                ved = stream->ved_pipeline[stream->pipe_size];
                stream->ved_pipeline[stream->pipe_size] = NULL;

                if (!is_media_entity_v4l2_subdev(ved->ent))
                        continue;

                sd = media_entity_to_v4l2_subdev(ved->ent);
                /*
                 * Do not call .s_stream() to stop an already
                 * stopped/unstarted subdev.
                 */
                if (!v4l2_subdev_is_streaming(sd))
                        continue;
                v4l2_subdev_call(sd, video, s_stream, 0);
        }
}

/**
 * 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)
{
        struct media_entity *entity;
        struct video_device *vdev;
        struct v4l2_subdev *sd;
        int ret = 0;

        stream->pipe_size = 0;
        while (stream->pipe_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);
                        ret = v4l2_subdev_call(sd, video, s_stream, 1);
                        if (ret && ret != -ENOIOCTLCMD) {
                                dev_err(ved->dev, "subdev_call error %s\n",
                                        ved->ent->name);
                                vimc_streamer_pipeline_terminate(stream);
                                return ret;
                        }
                }

                entity = vimc_get_source_entity(ved->ent);
                /* Check if the end of the pipeline was reached */
                if (!entity) {
                        /* the first entity of the pipe should be source only */
                        if (!vimc_is_source(ved->ent)) {
                                dev_err(ved->dev,
                                        "first entity in the pipe '%s' is not a source\n",
                                        ved->ent->name);
                                vimc_streamer_pipeline_terminate(stream);
                                return -EPIPE;
                        }
                        return 0;
                }

                /* Get the next device in the pipeline */
                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);
                }
        }

        vimc_streamer_pipeline_terminate(stream);
        return -EINVAL;
}

/**
 * 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)
{
        struct vimc_stream *stream = data;
        u8 *frame = NULL;
        int i;

        set_freezable();

        for (;;) {
                try_to_freeze();
                if (kthread_should_stop())
                        break;

                for (i = stream->pipe_size - 1; i >= 0; i--) {
                        frame = stream->ved_pipeline[i]->process_frame(
                                        stream->ved_pipeline[i], frame);
                        if (!frame || IS_ERR(frame))
                                break;
                }
                //wait for 60hz
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(HZ / 60);
        }

        return 0;
}

/**
 * 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)
{
        int ret;

        if (!stream || !ved)
                return -EINVAL;

        if (enable) {
                if (stream->kthread)
                        return 0;

                ret = vimc_streamer_pipeline_init(stream, ved);
                if (ret)
                        return ret;

                stream->kthread = kthread_run(vimc_streamer_thread, stream,
                                              "vimc-streamer thread");

                if (IS_ERR(stream->kthread)) {
                        ret = PTR_ERR(stream->kthread);
                        dev_err(ved->dev, "kthread_run failed with %d\n", ret);
                        vimc_streamer_pipeline_terminate(stream);
                        stream->kthread = NULL;
                        return ret;
                }

        } else {
                if (!stream->kthread)
                        return 0;

                ret = kthread_stop(stream->kthread);
                /*
                 * kthread_stop returns -EINTR in cases when streamon was
                 * immediately followed by streamoff, and the thread didn't had
                 * a chance to run. Ignore errors to stop the stream in the
                 * pipeline.
                 */
                if (ret)
                        dev_dbg(ved->dev, "kthread_stop returned '%d'\n", ret);

                stream->kthread = NULL;

                vimc_streamer_pipeline_terminate(stream);
        }

        return 0;
}