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From:   "Lucas A. M. Magalhaes" <lucmaga@gmail.com>
To:     linux-media@vger.kernel.org
Cc:     helen.koike@collabora.com, hverkuil@xs4all.nl, mchehab@kernel.org,
        lkcamp@lists.libreplanetbr.org, linux-kernel@vger.kernel.org,
        "Lucas A . M . Magalhaes" <lucmaga@gmail.com>,
        stable@vger.kernel.org
Subject: [PATCH v3] media: vimc: Add vimc-streamer for stream control
Date:   Thu, 17 Jan 2019 20:15:42 -0200
Message-Id: <20190117221542.24626-1-lucmaga@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add a linear pipeline logic for the stream control. It's created by
walking backwards on the entity graph. When the stream starts it will
simply loop through the pipeline calling the respective process_frame
function of each entity.

Fixes: f2fe89061d797 ("vimc: Virtual Media Controller core, capture
and sensor")
Cc: stable@vger.kernel.org # for v4.20
Signed-off-by: Lucas A. M. Magalhães <lucmaga@gmail.com>
---

The actual approach for streaming frames on vimc uses a recursive
logic[1]. This algorithm may cause problems as the stack usage
increases a with the topology. For the actual topology almost 1Kb of
stack is used if compiled with KASAN on a 64bit architecture. However
the topology is fixed and hard-coded on vimc-core[2]. So it's a
controlled situation if used as is.

[1]
The stream starts on vim-sensor's thread
https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-sensor.c#n204
It proceeds calling successively vimc_propagate_frame
https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-common.c#n210
Then processes_frame on the next entity
https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-scaler.c#n349
https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-debayer.c#n483
This goes until the loop ends on a vimc-capture device
https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-capture.c#n358

[2]https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-core.c#n80

Change since v2:
- Fix checks on vimc_streamer_pipeline_init.

 drivers/media/platform/vimc/Makefile        |   3 +-
 drivers/media/platform/vimc/vimc-capture.c  |  18 +-
 drivers/media/platform/vimc/vimc-common.c   |  35 ----
 drivers/media/platform/vimc/vimc-common.h   |  15 +-
 drivers/media/platform/vimc/vimc-debayer.c  |  26 +--
 drivers/media/platform/vimc/vimc-scaler.c   |  28 +--
 drivers/media/platform/vimc/vimc-sensor.c   |  56 ++----
 drivers/media/platform/vimc/vimc-streamer.c | 198 ++++++++++++++++++++
 drivers/media/platform/vimc/vimc-streamer.h |  38 ++++
 9 files changed, 270 insertions(+), 147 deletions(-)
 create mode 100644 drivers/media/platform/vimc/vimc-streamer.c
 create mode 100644 drivers/media/platform/vimc/vimc-streamer.h

diff --git a/drivers/media/platform/vimc/Makefile b/drivers/media/platform/vimc/Makefile
index 4b2e3de7856e..c4fc8e7d365a 100644
--- a/drivers/media/platform/vimc/Makefile
+++ b/drivers/media/platform/vimc/Makefile
@@ -5,6 +5,7 @@ vimc_common-objs := vimc-common.o
 vimc_debayer-objs := vimc-debayer.o
 vimc_scaler-objs := vimc-scaler.o
 vimc_sensor-objs := vimc-sensor.o
+vimc_streamer-objs := vimc-streamer.o
 
 obj-$(CONFIG_VIDEO_VIMC) += vimc.o vimc_capture.o vimc_common.o vimc-debayer.o \
-				vimc_scaler.o vimc_sensor.o
+			    vimc_scaler.o vimc_sensor.o vimc_streamer.o
diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
index 3f7e9ed56633..80d7515ec420 100644
--- a/drivers/media/platform/vimc/vimc-capture.c
+++ b/drivers/media/platform/vimc/vimc-capture.c
@@ -24,6 +24,7 @@
 #include <media/videobuf2-vmalloc.h>
 
 #include "vimc-common.h"
+#include "vimc-streamer.h"
 
 #define VIMC_CAP_DRV_NAME "vimc-capture"
 
@@ -44,7 +45,7 @@ struct vimc_cap_device {
 	spinlock_t qlock;
 	struct mutex lock;
 	u32 sequence;
-	struct media_pipeline pipe;
+	struct vimc_stream stream;
 };
 
 static const struct v4l2_pix_format fmt_default = {
@@ -248,14 +249,13 @@ static int vimc_cap_start_streaming(struct vb2_queue *vq, unsigned int count)
 	vcap->sequence = 0;
 
 	/* Start the media pipeline */
-	ret = media_pipeline_start(entity, &vcap->pipe);
+	ret = media_pipeline_start(entity, &vcap->stream.pipe);
 	if (ret) {
 		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
 		return ret;
 	}
 
-	/* Enable streaming from the pipe */
-	ret = vimc_pipeline_s_stream(&vcap->vdev.entity, 1);
+	ret = vimc_streamer_s_stream(&vcap->stream, &vcap->ved, 1);
 	if (ret) {
 		media_pipeline_stop(entity);
 		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
@@ -273,8 +273,7 @@ static void vimc_cap_stop_streaming(struct vb2_queue *vq)
 {
 	struct vimc_cap_device *vcap = vb2_get_drv_priv(vq);
 
-	/* Disable streaming from the pipe */
-	vimc_pipeline_s_stream(&vcap->vdev.entity, 0);
+	vimc_streamer_s_stream(&vcap->stream, &vcap->ved, 0);
 
 	/* Stop the media pipeline */
 	media_pipeline_stop(&vcap->vdev.entity);
@@ -355,8 +354,8 @@ static void vimc_cap_comp_unbind(struct device *comp, struct device *master,
 	kfree(vcap);
 }
 
-static void vimc_cap_process_frame(struct vimc_ent_device *ved,
-				   struct media_pad *sink, const void *frame)
+static void *vimc_cap_process_frame(struct vimc_ent_device *ved,
+				    const void *frame)
 {
 	struct vimc_cap_device *vcap = container_of(ved, struct vimc_cap_device,
 						    ved);
@@ -370,7 +369,7 @@ static void vimc_cap_process_frame(struct vimc_ent_device *ved,
 					    typeof(*vimc_buf), list);
 	if (!vimc_buf) {
 		spin_unlock(&vcap->qlock);
-		return;
+		return ERR_PTR(-EAGAIN);
 	}
 
 	/* Remove this entry from the list */
@@ -391,6 +390,7 @@ static void vimc_cap_process_frame(struct vimc_ent_device *ved,
 	vb2_set_plane_payload(&vimc_buf->vb2.vb2_buf, 0,
 			      vcap->format.sizeimage);
 	vb2_buffer_done(&vimc_buf->vb2.vb2_buf, VB2_BUF_STATE_DONE);
+	return NULL;
 }
 
 static int vimc_cap_comp_bind(struct device *comp, struct device *master,
diff --git a/drivers/media/platform/vimc/vimc-common.c b/drivers/media/platform/vimc/vimc-common.c
index 867e24dbd6b5..c1a74bb2df58 100644
--- a/drivers/media/platform/vimc/vimc-common.c
+++ b/drivers/media/platform/vimc/vimc-common.c
@@ -207,41 +207,6 @@ const struct vimc_pix_map *vimc_pix_map_by_pixelformat(u32 pixelformat)
 }
 EXPORT_SYMBOL_GPL(vimc_pix_map_by_pixelformat);
 
-int vimc_propagate_frame(struct media_pad *src, const void *frame)
-{
-	struct media_link *link;
-
-	if (!(src->flags & MEDIA_PAD_FL_SOURCE))
-		return -EINVAL;
-
-	/* Send this frame to all sink pads that are direct linked */
-	list_for_each_entry(link, &src->entity->links, list) {
-		if (link->source == src &&
-		    (link->flags & MEDIA_LNK_FL_ENABLED)) {
-			struct vimc_ent_device *ved = NULL;
-			struct media_entity *entity = link->sink->entity;
-
-			if (is_media_entity_v4l2_subdev(entity)) {
-				struct v4l2_subdev *sd =
-					container_of(entity, struct v4l2_subdev,
-						     entity);
-				ved = v4l2_get_subdevdata(sd);
-			} else if (is_media_entity_v4l2_video_device(entity)) {
-				struct video_device *vdev =
-					container_of(entity,
-						     struct video_device,
-						     entity);
-				ved = video_get_drvdata(vdev);
-			}
-			if (ved && ved->process_frame)
-				ved->process_frame(ved, link->sink, frame);
-		}
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(vimc_propagate_frame);
-
 /* Helper function to allocate and initialize pads */
 struct media_pad *vimc_pads_init(u16 num_pads, const unsigned long *pads_flag)
 {
diff --git a/drivers/media/platform/vimc/vimc-common.h b/drivers/media/platform/vimc/vimc-common.h
index 2e9981b18166..6ed969d9efbb 100644
--- a/drivers/media/platform/vimc/vimc-common.h
+++ b/drivers/media/platform/vimc/vimc-common.h
@@ -113,23 +113,12 @@ struct vimc_pix_map {
 struct vimc_ent_device {
 	struct media_entity *ent;
 	struct media_pad *pads;
-	void (*process_frame)(struct vimc_ent_device *ved,
-			      struct media_pad *sink, const void *frame);
+	void * (*process_frame)(struct vimc_ent_device *ved,
+				const void *frame);
 	void (*vdev_get_format)(struct vimc_ent_device *ved,
 			      struct v4l2_pix_format *fmt);
 };
 
-/**
- * vimc_propagate_frame - propagate a frame through the topology
- *
- * @src:	the source pad where the frame is being originated
- * @frame:	the frame to be propagated
- *
- * This function will call the process_frame callback from the vimc_ent_device
- * struct of the nodes directly connected to the @src pad
- */
-int vimc_propagate_frame(struct media_pad *src, const void *frame);
-
 /**
  * vimc_pads_init - initialize pads
  *
diff --git a/drivers/media/platform/vimc/vimc-debayer.c b/drivers/media/platform/vimc/vimc-debayer.c
index 77887f66f323..7d77c63b99d2 100644
--- a/drivers/media/platform/vimc/vimc-debayer.c
+++ b/drivers/media/platform/vimc/vimc-debayer.c
@@ -321,7 +321,6 @@ static void vimc_deb_set_rgb_mbus_fmt_rgb888_1x24(struct vimc_deb_device *vdeb,
 static int vimc_deb_s_stream(struct v4l2_subdev *sd, int enable)
 {
 	struct vimc_deb_device *vdeb = v4l2_get_subdevdata(sd);
-	int ret;
 
 	if (enable) {
 		const struct vimc_pix_map *vpix;
@@ -351,22 +350,10 @@ static int vimc_deb_s_stream(struct v4l2_subdev *sd, int enable)
 		if (!vdeb->src_frame)
 			return -ENOMEM;
 
-		/* Turn the stream on in the subdevices directly connected */
-		ret = vimc_pipeline_s_stream(&vdeb->sd.entity, 1);
-		if (ret) {
-			vfree(vdeb->src_frame);
-			vdeb->src_frame = NULL;
-			return ret;
-		}
 	} else {
 		if (!vdeb->src_frame)
 			return 0;
 
-		/* Disable streaming from the pipe */
-		ret = vimc_pipeline_s_stream(&vdeb->sd.entity, 0);
-		if (ret)
-			return ret;
-
 		vfree(vdeb->src_frame);
 		vdeb->src_frame = NULL;
 	}
@@ -480,9 +467,8 @@ static void vimc_deb_calc_rgb_sink(struct vimc_deb_device *vdeb,
 	}
 }
 
-static void vimc_deb_process_frame(struct vimc_ent_device *ved,
-				   struct media_pad *sink,
-				   const void *sink_frame)
+static void *vimc_deb_process_frame(struct vimc_ent_device *ved,
+				    const void *sink_frame)
 {
 	struct vimc_deb_device *vdeb = container_of(ved, struct vimc_deb_device,
 						    ved);
@@ -491,7 +477,7 @@ static void vimc_deb_process_frame(struct vimc_ent_device *ved,
 
 	/* If the stream in this node is not active, just return */
 	if (!vdeb->src_frame)
-		return;
+		return ERR_PTR(-EINVAL);
 
 	for (i = 0; i < vdeb->sink_fmt.height; i++)
 		for (j = 0; j < vdeb->sink_fmt.width; j++) {
@@ -499,12 +485,8 @@ static void vimc_deb_process_frame(struct vimc_ent_device *ved,
 			vdeb->set_rgb_src(vdeb, i, j, rgb);
 		}
 
-	/* Propagate the frame through all source pads */
-	for (i = 1; i < vdeb->sd.entity.num_pads; i++) {
-		struct media_pad *pad = &vdeb->sd.entity.pads[i];
+	return vdeb->src_frame;
 
-		vimc_propagate_frame(pad, vdeb->src_frame);
-	}
 }
 
 static void vimc_deb_comp_unbind(struct device *comp, struct device *master,
diff --git a/drivers/media/platform/vimc/vimc-scaler.c b/drivers/media/platform/vimc/vimc-scaler.c
index b0952ee86296..39b2a73dfcc1 100644
--- a/drivers/media/platform/vimc/vimc-scaler.c
+++ b/drivers/media/platform/vimc/vimc-scaler.c
@@ -217,7 +217,6 @@ static const struct v4l2_subdev_pad_ops vimc_sca_pad_ops = {
 static int vimc_sca_s_stream(struct v4l2_subdev *sd, int enable)
 {
 	struct vimc_sca_device *vsca = v4l2_get_subdevdata(sd);
-	int ret;
 
 	if (enable) {
 		const struct vimc_pix_map *vpix;
@@ -245,22 +244,10 @@ static int vimc_sca_s_stream(struct v4l2_subdev *sd, int enable)
 		if (!vsca->src_frame)
 			return -ENOMEM;
 
-		/* Turn the stream on in the subdevices directly connected */
-		ret = vimc_pipeline_s_stream(&vsca->sd.entity, 1);
-		if (ret) {
-			vfree(vsca->src_frame);
-			vsca->src_frame = NULL;
-			return ret;
-		}
 	} else {
 		if (!vsca->src_frame)
 			return 0;
 
-		/* Disable streaming from the pipe */
-		ret = vimc_pipeline_s_stream(&vsca->sd.entity, 0);
-		if (ret)
-			return ret;
-
 		vfree(vsca->src_frame);
 		vsca->src_frame = NULL;
 	}
@@ -346,26 +333,19 @@ static void vimc_sca_fill_src_frame(const struct vimc_sca_device *const vsca,
 			vimc_sca_scale_pix(vsca, i, j, sink_frame);
 }
 
-static void vimc_sca_process_frame(struct vimc_ent_device *ved,
-				   struct media_pad *sink,
-				   const void *sink_frame)
+static void *vimc_sca_process_frame(struct vimc_ent_device *ved,
+				    const void *sink_frame)
 {
 	struct vimc_sca_device *vsca = container_of(ved, struct vimc_sca_device,
 						    ved);
-	unsigned int i;
 
 	/* If the stream in this node is not active, just return */
 	if (!vsca->src_frame)
-		return;
+		return ERR_PTR(-EINVAL);
 
 	vimc_sca_fill_src_frame(vsca, sink_frame);
 
-	/* Propagate the frame through all source pads */
-	for (i = 1; i < vsca->sd.entity.num_pads; i++) {
-		struct media_pad *pad = &vsca->sd.entity.pads[i];
-
-		vimc_propagate_frame(pad, vsca->src_frame);
-	}
+	return vsca->src_frame;
 };
 
 static void vimc_sca_comp_unbind(struct device *comp, struct device *master,
diff --git a/drivers/media/platform/vimc/vimc-sensor.c b/drivers/media/platform/vimc/vimc-sensor.c
index 32ca9c6172b1..93961a1e694f 100644
--- a/drivers/media/platform/vimc/vimc-sensor.c
+++ b/drivers/media/platform/vimc/vimc-sensor.c
@@ -16,8 +16,6 @@
  */
 
 #include <linux/component.h>
-#include <linux/freezer.h>
-#include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
@@ -201,38 +199,27 @@ static const struct v4l2_subdev_pad_ops vimc_sen_pad_ops = {
 	.set_fmt		= vimc_sen_set_fmt,
 };
 
-static int vimc_sen_tpg_thread(void *data)
+static void *vimc_sen_process_frame(struct vimc_ent_device *ved,
+				    const void *sink_frame)
 {
-	struct vimc_sen_device *vsen = data;
-	unsigned int i;
-
-	set_freezable();
-	set_current_state(TASK_UNINTERRUPTIBLE);
-
-	for (;;) {
-		try_to_freeze();
-		if (kthread_should_stop())
-			break;
-
-		tpg_fill_plane_buffer(&vsen->tpg, 0, 0, vsen->frame);
+	struct vimc_sen_device *vsen = container_of(ved, struct vimc_sen_device,
+						    ved);
+	const struct vimc_pix_map *vpix;
+	unsigned int frame_size;
 
-		/* Send the frame to all source pads */
-		for (i = 0; i < vsen->sd.entity.num_pads; i++)
-			vimc_propagate_frame(&vsen->sd.entity.pads[i],
-					     vsen->frame);
+	/* Calculate the frame size */
+	vpix = vimc_pix_map_by_code(vsen->mbus_format.code);
+	frame_size = vsen->mbus_format.width * vpix->bpp *
+		     vsen->mbus_format.height;
 
-		/* 60 frames per second */
-		schedule_timeout(HZ/60);
-	}
-
-	return 0;
+	tpg_fill_plane_buffer(&vsen->tpg, 0, 0, vsen->frame);
+	return vsen->frame;
 }
 
 static int vimc_sen_s_stream(struct v4l2_subdev *sd, int enable)
 {
 	struct vimc_sen_device *vsen =
 				container_of(sd, struct vimc_sen_device, sd);
-	int ret;
 
 	if (enable) {
 		const struct vimc_pix_map *vpix;
@@ -258,26 +245,8 @@ static int vimc_sen_s_stream(struct v4l2_subdev *sd, int enable)
 		/* configure the test pattern generator */
 		vimc_sen_tpg_s_format(vsen);
 
-		/* Initialize the image generator thread */
-		vsen->kthread_sen = kthread_run(vimc_sen_tpg_thread, vsen,
-					"%s-sen", vsen->sd.v4l2_dev->name);
-		if (IS_ERR(vsen->kthread_sen)) {
-			dev_err(vsen->dev, "%s: kernel_thread() failed\n",
-				vsen->sd.name);
-			vfree(vsen->frame);
-			vsen->frame = NULL;
-			return PTR_ERR(vsen->kthread_sen);
-		}
 	} else {
-		if (!vsen->kthread_sen)
-			return 0;
-
-		/* Stop image generator */
-		ret = kthread_stop(vsen->kthread_sen);
-		if (ret)
-			return ret;
 
-		vsen->kthread_sen = NULL;
 		vfree(vsen->frame);
 		vsen->frame = NULL;
 		return 0;
@@ -413,6 +382,7 @@ static int vimc_sen_comp_bind(struct device *comp, struct device *master,
 	if (ret)
 		goto err_free_hdl;
 
+	vsen->ved.process_frame = vimc_sen_process_frame;
 	dev_set_drvdata(comp, &vsen->ved);
 	vsen->dev = comp;
 
diff --git a/drivers/media/platform/vimc/vimc-streamer.c b/drivers/media/platform/vimc/vimc-streamer.c
new file mode 100644
index 000000000000..7277cb07c7f4
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-streamer.c
@@ -0,0 +1,198 @@
+// 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/module.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.
+ */
+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_entity_remote_pad(&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 media_entity *entity;
+	struct v4l2_subdev *sd;
+
+	do {
+		stream->pipe_size--;
+		entity = stream->ved_pipeline[stream->pipe_size]->ent;
+		entity = vimc_get_source_entity(entity);
+		stream->ved_pipeline[stream->pipe_size] = NULL;
+		/*
+		 *  This may occur only if the streamer was not correctly
+		 *  initialized.
+		 */
+		if (!entity)
+			continue;
+
+		if (!is_media_entity_v4l2_subdev(entity))
+			continue;
+
+		sd = media_entity_to_v4l2_subdev(entity);
+		v4l2_subdev_call(sd, video, s_stream, 0);
+	} while (stream->pipe_size);
+}
+
+/*
+ * 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 s_stream to enable stream in all entities of the pipeline.
+ */
+static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
+				struct vimc_ent_device *ved)
+{
+	struct vimc_ent_device *source_ved;
+	struct media_entity *entity;
+	struct video_device *vdev;
+	struct v4l2_subdev *sd;
+	int ret = -EINVAL;
+
+	stream->pipe_size = 0;
+	stream->ved_pipeline[stream->pipe_size++] = ved;
+
+	while (stream->pipe_size < VIMC_STREAMER_PIPELINE_MAX_SIZE) {
+		entity = stream->ved_pipeline[stream->pipe_size-1]->ent;
+		entity = vimc_get_source_entity(entity);
+		if (!entity)
+			return 0;
+		if (is_media_entity_v4l2_subdev(entity)) {
+			sd = media_entity_to_v4l2_subdev(entity);
+			ret = v4l2_subdev_call(sd, video, s_stream, 1);
+			if (ret && ret != -ENOIOCTLCMD)
+				break;
+			source_ved = v4l2_get_subdevdata(sd);
+		} else {
+			vdev = container_of(entity,
+					    struct video_device,
+					    entity);
+			source_ved = video_get_drvdata(vdev);
+		}
+
+		if (!source_ved)
+			break;
+
+		stream->ved_pipeline[stream->pipe_size++] = source_ved;
+	}
+
+	/*
+	 * If an error occurs during initialization or the pipeline gets longer
+	 * than VIMC_STREAMER_PIPELINE_MAX_SIZE the stream is disabled and
+	 * returns the error code.
+	 */
+	vimc_streamer_pipeline_terminate(stream);
+	return ret;
+}
+
+static int vimc_streamer_thread(void *data)
+{
+	struct vimc_stream *stream = data;
+	int i;
+
+	set_freezable();
+	set_current_state(TASK_UNINTERRUPTIBLE);
+
+	for (;;) {
+		try_to_freeze();
+		if (kthread_should_stop())
+			break;
+
+		for (i = stream->pipe_size - 1; i >= 0; i--) {
+			stream->frame = stream->ved_pipeline[i]->process_frame(
+					stream->ved_pipeline[i],
+					stream->frame);
+			if (!stream->frame)
+				break;
+			if (IS_ERR(stream->frame))
+				break;
+		}
+		//wait for 60hz
+		schedule_timeout(HZ / 60);
+	}
+
+	return 0;
+}
+
+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))
+			return PTR_ERR(stream->kthread);
+
+	} else {
+		if (!stream->kthread)
+			return 0;
+
+		ret = kthread_stop(stream->kthread);
+		if (ret)
+			return ret;
+
+		stream->kthread = NULL;
+
+		vimc_streamer_pipeline_terminate(stream);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vimc_streamer_s_stream);
+
+MODULE_DESCRIPTION("Virtual Media Controller Driver (VIMC) Streamer");
+MODULE_AUTHOR("Lucas A. M. Magalhães <lucmaga@gmail.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/media/platform/vimc/vimc-streamer.h b/drivers/media/platform/vimc/vimc-streamer.h
new file mode 100644
index 000000000000..752af2e2d5a2
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-streamer.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * vimc-streamer.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2018 Lucas A. M. Magalhães <lucmaga@gmail.com>
+ *
+ */
+
+#ifndef _VIMC_STREAMER_H_
+#define _VIMC_STREAMER_H_
+
+#include <media/media-device.h>
+
+#include "vimc-common.h"
+
+#define VIMC_STREAMER_PIPELINE_MAX_SIZE 16
+
+struct vimc_stream {
+	struct media_pipeline pipe;
+	struct vimc_ent_device *ved_pipeline[VIMC_STREAMER_PIPELINE_MAX_SIZE];
+	unsigned int pipe_size;
+	u8 *frame;
+	struct task_struct *kthread;
+};
+
+/**
+ * vimc_streamer_s_streamer - start/stop the stream
+ *
+ * @stream:	the pointer to the stream to start or stop
+ * @ved:	The last entity of the streamer pipeline
+ * @enable:	any non-zero number start the stream, zero stop
+ *
+ */
+int vimc_streamer_s_stream(struct vimc_stream *stream,
+			   struct vimc_ent_device *ved,
+			   int enable);
+
+#endif  //_VIMC_STREAMER_H_
-- 
2.20.0.rc1