[media] vimc: Virtual Media Controller core, capture and sensor

First version of the Virtual Media Controller.
Add a simple version of the core of the driver, the capture and
sensor nodes in the topology, generating a grey image in a hardcoded
format.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
[hans.verkuil@cisco.com: fix small typo in Kconfig]

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

MAINTAINERS

@@ -13407,6 +13407,14 @@ W:	https://linuxtv.org
 S:	Maintained
 F:	drivers/media/platform/vivid/*
 
+VIMC VIRTUAL MEDIA CONTROLLER DRIVER
+M:	Helen Koike <helen.koike@collabora.com>
+L:	linux-media@vger.kernel.org
+T:	git git://linuxtv.org/media_tree.git
+W:	https://linuxtv.org
+S:	Maintained
+F:	drivers/media/platform/vimc/*
+
 VLYNQ BUS
 M:	Florian Fainelli <f.fainelli@gmail.com>
 L:	openwrt-devel@lists.openwrt.org (subscribers-only)

drivers/media/platform/Kconfig

@@ -495,6 +495,8 @@ menuconfig V4L_TEST_DRIVERS
 
 if V4L_TEST_DRIVERS
 
+source "drivers/media/platform/vimc/Kconfig"
+
 source "drivers/media/platform/vivid/Kconfig"
 
 config VIDEO_VIM2M

drivers/media/platform/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_VIDEO_PXA27x)	+= pxa_camera.o
 
 obj-$(CONFIG_VIDEO_VIU) += fsl-viu.o
 
+obj-$(CONFIG_VIDEO_VIMC)		+= vimc/
 obj-$(CONFIG_VIDEO_VIVID)		+= vivid/
 obj-$(CONFIG_VIDEO_VIM2M)		+= vim2m.o
 

drivers/media/platform/vimc/Kconfig

@@ -0,0 +1,14 @@
+config VIDEO_VIMC
+	tristate "Virtual Media Controller Driver (VIMC)"
+	depends on VIDEO_DEV && VIDEO_V4L2 && VIDEO_V4L2_SUBDEV_API
+	select VIDEOBUF2_VMALLOC
+	default n
+	---help---
+	  Skeleton driver for Virtual Media Controller
+
+	  This driver can be compared to the vivid driver for emulating
+	  a media node that exposes a complex media topology. The topology
+	  is hard coded for now but is meant to be highly configurable in
+	  the future.
+
+	  When in doubt, say N.

drivers/media/platform/vimc/Makefile

@@ -0,0 +1,3 @@
+vimc-objs := vimc-core.o vimc-capture.o vimc-sensor.o
+
+obj-$(CONFIG_VIDEO_VIMC) += vimc.o

drivers/media/platform/vimc/vimc-capture.c

@@ -0,0 +1,498 @@
+/*
+ * vimc-capture.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <media/v4l2-ioctl.h>
+#include <media/videobuf2-core.h>
+#include <media/videobuf2-vmalloc.h>
+
+#include "vimc-capture.h"
+
+struct vimc_cap_device {
+	struct vimc_ent_device ved;
+	struct video_device vdev;
+	struct v4l2_pix_format format;
+	struct vb2_queue queue;
+	struct list_head buf_list;
+	/*
+	 * NOTE: in a real driver, a spin lock must be used to access the
+	 * queue because the frames are generated from a hardware interruption
+	 * and the isr is not allowed to sleep.
+	 * Even if it is not necessary a spinlock in the vimc driver, we
+	 * use it here as a code reference
+	 */
+	spinlock_t qlock;
+	struct mutex lock;
+	u32 sequence;
+	struct media_pipeline pipe;
+};
+
+struct vimc_cap_buffer {
+	/*
+	 * struct vb2_v4l2_buffer must be the first element
+	 * the videobuf2 framework will allocate this struct based on
+	 * buf_struct_size and use the first sizeof(struct vb2_buffer) bytes of
+	 * memory as a vb2_buffer
+	 */
+	struct vb2_v4l2_buffer vb2;
+	struct list_head list;
+};
+
+static int vimc_cap_querycap(struct file *file, void *priv,
+			     struct v4l2_capability *cap)
+{
+	struct vimc_cap_device *vcap = video_drvdata(file);
+
+	strlcpy(cap->driver, KBUILD_MODNAME, sizeof(cap->driver));
+	strlcpy(cap->card, KBUILD_MODNAME, sizeof(cap->card));
+	snprintf(cap->bus_info, sizeof(cap->bus_info),
+		 "platform:%s", vcap->vdev.v4l2_dev->name);
+
+	return 0;
+}
+
+static int vimc_cap_fmt_vid_cap(struct file *file, void *priv,
+				  struct v4l2_format *f)
+{
+	struct vimc_cap_device *vcap = video_drvdata(file);
+
+	f->fmt.pix = vcap->format;
+
+	return 0;
+}
+
+static int vimc_cap_enum_fmt_vid_cap(struct file *file, void *priv,
+				     struct v4l2_fmtdesc *f)
+{
+	struct vimc_cap_device *vcap = video_drvdata(file);
+
+	if (f->index > 0)
+		return -EINVAL;
+
+	/* We only support one format for now */
+	f->pixelformat = vcap->format.pixelformat;
+
+	return 0;
+}
+
+static const struct v4l2_file_operations vimc_cap_fops = {
+	.owner		= THIS_MODULE,
+	.open		= v4l2_fh_open,
+	.release	= vb2_fop_release,
+	.read           = vb2_fop_read,
+	.poll		= vb2_fop_poll,
+	.unlocked_ioctl = video_ioctl2,
+	.mmap           = vb2_fop_mmap,
+};
+
+static const struct v4l2_ioctl_ops vimc_cap_ioctl_ops = {
+	.vidioc_querycap = vimc_cap_querycap,
+
+	.vidioc_g_fmt_vid_cap = vimc_cap_fmt_vid_cap,
+	.vidioc_s_fmt_vid_cap = vimc_cap_fmt_vid_cap,
+	.vidioc_try_fmt_vid_cap = vimc_cap_fmt_vid_cap,
+	.vidioc_enum_fmt_vid_cap = vimc_cap_enum_fmt_vid_cap,
+
+	.vidioc_reqbufs = vb2_ioctl_reqbufs,
+	.vidioc_create_bufs = vb2_ioctl_create_bufs,
+	.vidioc_prepare_buf = vb2_ioctl_prepare_buf,
+	.vidioc_querybuf = vb2_ioctl_querybuf,
+	.vidioc_qbuf = vb2_ioctl_qbuf,
+	.vidioc_dqbuf = vb2_ioctl_dqbuf,
+	.vidioc_expbuf = vb2_ioctl_expbuf,
+	.vidioc_streamon = vb2_ioctl_streamon,
+	.vidioc_streamoff = vb2_ioctl_streamoff,
+};
+
+static void vimc_cap_return_all_buffers(struct vimc_cap_device *vcap,
+					enum vb2_buffer_state state)
+{
+	struct vimc_cap_buffer *vbuf, *node;
+
+	spin_lock(&vcap->qlock);
+
+	list_for_each_entry_safe(vbuf, node, &vcap->buf_list, list) {
+		list_del(&vbuf->list);
+		vb2_buffer_done(&vbuf->vb2.vb2_buf, state);
+	}
+
+	spin_unlock(&vcap->qlock);
+}
+
+static int vimc_cap_pipeline_s_stream(struct vimc_cap_device *vcap, int enable)
+{
+	struct v4l2_subdev *sd;
+	struct media_pad *pad;
+	int ret;
+
+	/* Start the stream in the subdevice direct connected */
+	pad = media_entity_remote_pad(&vcap->vdev.entity.pads[0]);
+
+	/*
+	 * if it is a raw node from vimc-core, there is nothing to activate
+	 * TODO: remove this when there are no more raw nodes in the
+	 * core and return error instead
+	 */
+	if (pad->entity->obj_type == MEDIA_ENTITY_TYPE_BASE)
+		return 0;
+
+	sd = media_entity_to_v4l2_subdev(pad->entity);
+	ret = v4l2_subdev_call(sd, video, s_stream, enable);
+	if (ret && ret != -ENOIOCTLCMD)
+		return ret;
+
+	return 0;
+}
+
+static int vimc_cap_start_streaming(struct vb2_queue *vq, unsigned int count)
+{
+	struct vimc_cap_device *vcap = vb2_get_drv_priv(vq);
+	struct media_entity *entity = &vcap->vdev.entity;
+	int ret;
+
+	vcap->sequence = 0;
+
+	/* Start the media pipeline */
+	ret = media_pipeline_start(entity, &vcap->pipe);
+	if (ret) {
+		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
+		return ret;
+	}
+
+	/* Enable streaming from the pipe */
+	ret = vimc_cap_pipeline_s_stream(vcap, 1);
+	if (ret) {
+		media_pipeline_stop(entity);
+		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
+		return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * Stop the stream engine. Any remaining buffers in the stream queue are
+ * dequeued and passed on to the vb2 framework marked as STATE_ERROR.
+ */
+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_cap_pipeline_s_stream(vcap, 0);
+
+	/* Stop the media pipeline */
+	media_pipeline_stop(&vcap->vdev.entity);
+
+	/* Release all active buffers */
+	vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_ERROR);
+}
+
+static void vimc_cap_buf_queue(struct vb2_buffer *vb2_buf)
+{
+	struct vimc_cap_device *vcap = vb2_get_drv_priv(vb2_buf->vb2_queue);
+	struct vimc_cap_buffer *buf = container_of(vb2_buf,
+						   struct vimc_cap_buffer,
+						   vb2.vb2_buf);
+
+	spin_lock(&vcap->qlock);
+	list_add_tail(&buf->list, &vcap->buf_list);
+	spin_unlock(&vcap->qlock);
+}
+
+static int vimc_cap_queue_setup(struct vb2_queue *vq, unsigned int *nbuffers,
+				unsigned int *nplanes, unsigned int sizes[],
+				struct device *alloc_devs[])
+{
+	struct vimc_cap_device *vcap = vb2_get_drv_priv(vq);
+
+	if (*nplanes)
+		return sizes[0] < vcap->format.sizeimage ? -EINVAL : 0;
+	/* We don't support multiplanes for now */
+	*nplanes = 1;
+	sizes[0] = vcap->format.sizeimage;
+
+	return 0;
+}
+
+static int vimc_cap_buffer_prepare(struct vb2_buffer *vb)
+{
+	struct vimc_cap_device *vcap = vb2_get_drv_priv(vb->vb2_queue);
+	unsigned long size = vcap->format.sizeimage;
+
+	if (vb2_plane_size(vb, 0) < size) {
+		dev_err(vcap->vdev.v4l2_dev->dev,
+			"%s: buffer too small (%lu < %lu)\n",
+			vcap->vdev.name, vb2_plane_size(vb, 0), size);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static const struct vb2_ops vimc_cap_qops = {
+	.start_streaming	= vimc_cap_start_streaming,
+	.stop_streaming		= vimc_cap_stop_streaming,
+	.buf_queue		= vimc_cap_buf_queue,
+	.queue_setup		= vimc_cap_queue_setup,
+	.buf_prepare		= vimc_cap_buffer_prepare,
+	/*
+	 * Since q->lock is set we can use the standard
+	 * vb2_ops_wait_prepare/finish helper functions.
+	 */
+	.wait_prepare		= vb2_ops_wait_prepare,
+	.wait_finish		= vb2_ops_wait_finish,
+};
+
+/*
+ * NOTE: this function is a copy of v4l2_subdev_link_validate_get_format
+ * maybe the v4l2 function should be public
+ */
+static int vimc_cap_v4l2_subdev_link_validate_get_format(struct media_pad *pad,
+						struct v4l2_subdev_format *fmt)
+{
+	struct v4l2_subdev *sd = media_entity_to_v4l2_subdev(pad->entity);
+
+	fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
+	fmt->pad = pad->index;
+
+	return v4l2_subdev_call(sd, pad, get_fmt, NULL, fmt);
+}
+
+static int vimc_cap_link_validate(struct media_link *link)
+{
+	struct v4l2_subdev_format source_fmt;
+	const struct vimc_pix_map *vpix;
+	struct vimc_cap_device *vcap = container_of(link->sink->entity,
+						    struct vimc_cap_device,
+						    vdev.entity);
+	struct v4l2_pix_format *sink_fmt = &vcap->format;
+	int ret;
+
+	/*
+	 * if it is a raw node from vimc-core, ignore the link for now
+	 * TODO: remove this when there are no more raw nodes in the
+	 * core and return error instead
+	 */
+	if (link->source->entity->obj_type == MEDIA_ENTITY_TYPE_BASE)
+		return 0;
+
+	/* Get the the format of the subdev */
+	ret = vimc_cap_v4l2_subdev_link_validate_get_format(link->source,
+							    &source_fmt);
+	if (ret)
+		return ret;
+
+	dev_dbg(vcap->vdev.v4l2_dev->dev,
+		"%s: link validate formats src:%dx%d %d sink:%dx%d %d\n",
+		vcap->vdev.name,
+		source_fmt.format.width, source_fmt.format.height,
+		source_fmt.format.code,
+		sink_fmt->width, sink_fmt->height,
+		sink_fmt->pixelformat);
+
+	/* The width, height and code must match. */
+	vpix = vimc_pix_map_by_pixelformat(sink_fmt->pixelformat);
+	if (source_fmt.format.width != sink_fmt->width
+	    || source_fmt.format.height != sink_fmt->height
+	    || vpix->code != source_fmt.format.code)
+		return -EPIPE;
+
+	/*
+	 * The field order must match, or the sink field order must be NONE
+	 * to support interlaced hardware connected to bridges that support
+	 * progressive formats only.
+	 */
+	if (source_fmt.format.field != sink_fmt->field &&
+	    sink_fmt->field != V4L2_FIELD_NONE)
+		return -EPIPE;
+
+	return 0;
+}
+
+static const struct media_entity_operations vimc_cap_mops = {
+	.link_validate		= vimc_cap_link_validate,
+};
+
+static void vimc_cap_destroy(struct vimc_ent_device *ved)
+{
+	struct vimc_cap_device *vcap = container_of(ved, struct vimc_cap_device,
+						    ved);
+
+	vb2_queue_release(&vcap->queue);
+	media_entity_cleanup(ved->ent);
+	video_unregister_device(&vcap->vdev);
+	vimc_pads_cleanup(vcap->ved.pads);
+	kfree(vcap);
+}
+
+static void vimc_cap_process_frame(struct vimc_ent_device *ved,
+				   struct media_pad *sink, const void *frame)
+{
+	struct vimc_cap_device *vcap = container_of(ved, struct vimc_cap_device,
+						    ved);
+	struct vimc_cap_buffer *vimc_buf;
+	void *vbuf;
+
+	spin_lock(&vcap->qlock);
+
+	/* Get the first entry of the list */
+	vimc_buf = list_first_entry_or_null(&vcap->buf_list,
+					    typeof(*vimc_buf), list);
+	if (!vimc_buf) {
+		spin_unlock(&vcap->qlock);
+		return;
+	}
+
+	/* Remove this entry from the list */
+	list_del(&vimc_buf->list);
+
+	spin_unlock(&vcap->qlock);
+
+	/* Fill the buffer */
+	vimc_buf->vb2.vb2_buf.timestamp = ktime_get_ns();
+	vimc_buf->vb2.sequence = vcap->sequence++;
+	vimc_buf->vb2.field = vcap->format.field;
+
+	vbuf = vb2_plane_vaddr(&vimc_buf->vb2.vb2_buf, 0);
+
+	memcpy(vbuf, frame, vcap->format.sizeimage);
+
+	/* Set it as ready */
+	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);
+}
+
+struct vimc_ent_device *vimc_cap_create(struct v4l2_device *v4l2_dev,
+					const char *const name,
+					u16 num_pads,
+					const unsigned long *pads_flag)
+{
+	const struct vimc_pix_map *vpix;
+	struct vimc_cap_device *vcap;
+	struct video_device *vdev;
+	struct vb2_queue *q;
+	int ret;
+
+	/*
+	 * Check entity configuration params
+	 * NOTE: we only support a single sink pad
+	 */
+	if (!name || num_pads != 1 || !pads_flag ||
+	    !(pads_flag[0] & MEDIA_PAD_FL_SINK))
+		return ERR_PTR(-EINVAL);
+
+	/* Allocate the vimc_cap_device struct */
+	vcap = kzalloc(sizeof(*vcap), GFP_KERNEL);
+	if (!vcap)
+		return ERR_PTR(-ENOMEM);
+
+	/* Allocate the pads */
+	vcap->ved.pads = vimc_pads_init(num_pads, pads_flag);
+	if (IS_ERR(vcap->ved.pads)) {
+		ret = PTR_ERR(vcap->ved.pads);
+		goto err_free_vcap;
+	}
+
+	/* Initialize the media entity */
+	vcap->vdev.entity.name = name;
+	vcap->vdev.entity.function = MEDIA_ENT_F_IO_V4L;
+	ret = media_entity_pads_init(&vcap->vdev.entity,
+				     num_pads, vcap->ved.pads);
+	if (ret)
+		goto err_clean_pads;
+
+	/* Initialize the lock */
+	mutex_init(&vcap->lock);
+
+	/* Initialize the vb2 queue */
+	q = &vcap->queue;
+	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	q->io_modes = VB2_MMAP | VB2_DMABUF;
+	q->drv_priv = vcap;
+	q->buf_struct_size = sizeof(struct vimc_cap_buffer);
+	q->ops = &vimc_cap_qops;
+	q->mem_ops = &vb2_vmalloc_memops;
+	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
+	q->min_buffers_needed = 2;
+	q->lock = &vcap->lock;
+
+	ret = vb2_queue_init(q);
+	if (ret) {
+		dev_err(vcap->vdev.v4l2_dev->dev,
+			"%s: vb2 queue init failed (err=%d)\n",
+			vcap->vdev.name, ret);
+		goto err_clean_m_ent;
+	}
+
+	/* Initialize buffer list and its lock */
+	INIT_LIST_HEAD(&vcap->buf_list);
+	spin_lock_init(&vcap->qlock);
+
+	/* Set the frame format (this is hardcoded for now) */
+	vcap->format.width = 640;
+	vcap->format.height = 480;
+	vcap->format.pixelformat = V4L2_PIX_FMT_RGB24;
+	vcap->format.field = V4L2_FIELD_NONE;
+	vcap->format.colorspace = V4L2_COLORSPACE_SRGB;
+
+	vpix = vimc_pix_map_by_pixelformat(vcap->format.pixelformat);
+
+	vcap->format.bytesperline = vcap->format.width * vpix->bpp;
+	vcap->format.sizeimage = vcap->format.bytesperline *
+				 vcap->format.height;
+
+	/* Fill the vimc_ent_device struct */
+	vcap->ved.destroy = vimc_cap_destroy;
+	vcap->ved.ent = &vcap->vdev.entity;
+	vcap->ved.process_frame = vimc_cap_process_frame;
+
+	/* Initialize the video_device struct */
+	vdev = &vcap->vdev;
+	vdev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
+	vdev->entity.ops = &vimc_cap_mops;
+	vdev->release = video_device_release_empty;
+	vdev->fops = &vimc_cap_fops;
+	vdev->ioctl_ops = &vimc_cap_ioctl_ops;
+	vdev->lock = &vcap->lock;
+	vdev->queue = q;
+	vdev->v4l2_dev = v4l2_dev;
+	vdev->vfl_dir = VFL_DIR_RX;
+	strlcpy(vdev->name, name, sizeof(vdev->name));
+	video_set_drvdata(vdev, &vcap->ved);
+
+	/* Register the video_device with the v4l2 and the media framework */
+	ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1);
+	if (ret) {
+		dev_err(vcap->vdev.v4l2_dev->dev,
+			"%s: video register failed (err=%d)\n",
+			vcap->vdev.name, ret);
+		goto err_release_queue;
+	}
+
+	return &vcap->ved;
+
+err_release_queue:
+	vb2_queue_release(q);
+err_clean_m_ent:
+	media_entity_cleanup(&vcap->vdev.entity);
+err_clean_pads:
+	vimc_pads_cleanup(vcap->ved.pads);
+err_free_vcap:
+	kfree(vcap);
+
+	return ERR_PTR(ret);
+}

drivers/media/platform/vimc/vimc-capture.h

@@ -0,0 +1,28 @@
+/*
+ * vimc-capture.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _VIMC_CAPTURE_H_
+#define _VIMC_CAPTURE_H_
+
+#include "vimc-core.h"
+
+struct vimc_ent_device *vimc_cap_create(struct v4l2_device *v4l2_dev,
+					const char *const name,
+					u16 num_pads,
+					const unsigned long *pads_flag);
+
+#endif

drivers/media/platform/vimc/vimc-core.h

@@ -0,0 +1,112 @@
+/*
+ * vimc-core.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _VIMC_CORE_H_
+#define _VIMC_CORE_H_
+
+#include <linux/slab.h>
+#include <media/v4l2-device.h>
+
+/**
+ * struct vimc_pix_map - maps media bus code with v4l2 pixel format
+ *
+ * @code:		media bus format code defined by MEDIA_BUS_FMT_* macros
+ * @bbp:		number of bytes each pixel occupies
+ * @pixelformat:	pixel format devined by V4L2_PIX_FMT_* macros
+ *
+ * Struct which matches the MEDIA_BUS_FMT_* codes with the corresponding
+ * V4L2_PIX_FMT_* fourcc pixelformat and its bytes per pixel (bpp)
+ */
+struct vimc_pix_map {
+	unsigned int code;
+	unsigned int bpp;
+	u32 pixelformat;
+};
+
+/**
+ * struct vimc_ent_device - core struct that represents a node in the topology
+ *
+ * @ent:		the pointer to struct media_entity for the node
+ * @pads:		the list of pads of the node
+ * @destroy:		callback to destroy the node
+ * @process_frame:	callback send a frame to that node
+ *
+ * Each node of the topology must create a vimc_ent_device struct. Depending on
+ * the node it will be of an instance of v4l2_subdev or video_device struct
+ * where both contains a struct media_entity.
+ * Those structures should embedded the vimc_ent_device struct through
+ * v4l2_set_subdevdata() and video_set_drvdata() respectivaly, allowing the
+ * vimc_ent_device struct to be retrieved from the corresponding struct
+ * media_entity
+ */
+struct vimc_ent_device {
+	struct media_entity *ent;
+	struct media_pad *pads;
+	void (*destroy)(struct vimc_ent_device *);
+	void (*process_frame)(struct vimc_ent_device *ved,
+			      struct media_pad *sink, const void *frame);
+};
+
+/**
+ * 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
+ *
+ * @num_pads:	number of pads to initialize
+ * @pads_flags:	flags to use in each pad
+ *
+ * Helper functions to allocate/initialize pads
+ */
+struct media_pad *vimc_pads_init(u16 num_pads,
+				 const unsigned long *pads_flag);
+
+/**
+ * vimc_pads_cleanup - free pads
+ *
+ * @pads: pointer to the pads
+ *
+ * Helper function to free the pads initialized with vimc_pads_init
+ */
+static inline void vimc_pads_cleanup(struct media_pad *pads)
+{
+	kfree(pads);
+}
+
+/**
+ * vimc_pix_map_by_code - get vimc_pix_map struct by media bus code
+ *
+ * @code:		media bus format code defined by MEDIA_BUS_FMT_* macros
+ */
+const struct vimc_pix_map *vimc_pix_map_by_code(u32 code);
+
+/**
+ * vimc_pix_map_by_pixelformat - get vimc_pix_map struct by v4l2 pixel format
+ *
+ * @pixelformat:	pixel format devined by V4L2_PIX_FMT_* macros
+ */
+const struct vimc_pix_map *vimc_pix_map_by_pixelformat(u32 pixelformat);
+
+#endif

drivers/media/platform/vimc/vimc-sensor.c

@@ -0,0 +1,276 @@
+/*
+ * vimc-sensor.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include <linux/v4l2-mediabus.h>
+#include <linux/vmalloc.h>
+#include <media/v4l2-subdev.h>
+
+#include "vimc-sensor.h"
+
+struct vimc_sen_device {
+	struct vimc_ent_device ved;
+	struct v4l2_subdev sd;
+	struct task_struct *kthread_sen;
+	u8 *frame;
+	/* The active format */
+	struct v4l2_mbus_framefmt mbus_format;
+	int frame_size;
+};
+
+static int vimc_sen_enum_mbus_code(struct v4l2_subdev *sd,
+				   struct v4l2_subdev_pad_config *cfg,
+				   struct v4l2_subdev_mbus_code_enum *code)
+{
+	struct vimc_sen_device *vsen =
+				container_of(sd, struct vimc_sen_device, sd);
+
+	/* TODO: Add support for other codes */
+	if (code->index)
+		return -EINVAL;
+
+	code->code = vsen->mbus_format.code;
+
+	return 0;
+}
+
+static int vimc_sen_enum_frame_size(struct v4l2_subdev *sd,
+				    struct v4l2_subdev_pad_config *cfg,
+				    struct v4l2_subdev_frame_size_enum *fse)
+{
+	struct vimc_sen_device *vsen =
+				container_of(sd, struct vimc_sen_device, sd);
+
+	/* TODO: Add support to other formats */
+	if (fse->index)
+		return -EINVAL;
+
+	/* TODO: Add support for other codes */
+	if (fse->code != vsen->mbus_format.code)
+		return -EINVAL;
+
+	fse->min_width = vsen->mbus_format.width;
+	fse->max_width = vsen->mbus_format.width;
+	fse->min_height = vsen->mbus_format.height;
+	fse->max_height = vsen->mbus_format.height;
+
+	return 0;
+}
+
+static int vimc_sen_get_fmt(struct v4l2_subdev *sd,
+			    struct v4l2_subdev_pad_config *cfg,
+			    struct v4l2_subdev_format *format)
+{
+	struct vimc_sen_device *vsen =
+				container_of(sd, struct vimc_sen_device, sd);
+
+	format->format = vsen->mbus_format;
+
+	return 0;
+}
+
+static const struct v4l2_subdev_pad_ops vimc_sen_pad_ops = {
+	.enum_mbus_code		= vimc_sen_enum_mbus_code,
+	.enum_frame_size	= vimc_sen_enum_frame_size,
+	.get_fmt		= vimc_sen_get_fmt,
+	/* TODO: Add support to other formats */
+	.set_fmt		= vimc_sen_get_fmt,
+};
+
+/* media operations */
+static const struct media_entity_operations vimc_sen_mops = {
+	.link_validate = v4l2_subdev_link_validate,
+};
+
+static int vimc_thread_sen(void *data)
+{
+	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;
+
+		memset(vsen->frame, 100, vsen->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);
+
+		/* 60 frames per second */
+		schedule_timeout(HZ/60);
+	}
+
+	return 0;
+}
+
+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;
+
+		if (vsen->kthread_sen)
+			return -EINVAL;
+
+		/* Calculate the frame size */
+		vpix = vimc_pix_map_by_code(vsen->mbus_format.code);
+		vsen->frame_size = vsen->mbus_format.width * vpix->bpp *
+				   vsen->mbus_format.height;
+
+		/*
+		 * Allocate the frame buffer. Use vmalloc to be able to
+		 * allocate a large amount of memory
+		 */
+		vsen->frame = vmalloc(vsen->frame_size);
+		if (!vsen->frame)
+			return -ENOMEM;
+
+		/* Initialize the image generator thread */
+		vsen->kthread_sen = kthread_run(vimc_thread_sen, vsen, "%s-sen",
+						vsen->sd.v4l2_dev->name);
+		if (IS_ERR(vsen->kthread_sen)) {
+			dev_err(vsen->sd.v4l2_dev->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 -EINVAL;
+
+		/* Stop image generator */
+		ret = kthread_stop(vsen->kthread_sen);
+		vsen->kthread_sen = NULL;
+
+		vfree(vsen->frame);
+		vsen->frame = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+struct v4l2_subdev_video_ops vimc_sen_video_ops = {
+	.s_stream = vimc_sen_s_stream,
+};
+
+static const struct v4l2_subdev_ops vimc_sen_ops = {
+	.pad = &vimc_sen_pad_ops,
+	.video = &vimc_sen_video_ops,
+};
+
+static void vimc_sen_destroy(struct vimc_ent_device *ved)
+{
+	struct vimc_sen_device *vsen =
+				container_of(ved, struct vimc_sen_device, ved);
+
+	v4l2_device_unregister_subdev(&vsen->sd);
+	media_entity_cleanup(ved->ent);
+	kfree(vsen);
+}
+
+struct vimc_ent_device *vimc_sen_create(struct v4l2_device *v4l2_dev,
+					const char *const name,
+					u16 num_pads,
+					const unsigned long *pads_flag)
+{
+	struct vimc_sen_device *vsen;
+	unsigned int i;
+	int ret;
+
+	/* NOTE: a sensor node may be created with more then one pad */
+	if (!name || !num_pads || !pads_flag)
+		return ERR_PTR(-EINVAL);
+
+	/* check if all pads are sources */
+	for (i = 0; i < num_pads; i++)
+		if (!(pads_flag[i] & MEDIA_PAD_FL_SOURCE))
+			return ERR_PTR(-EINVAL);
+
+	/* Allocate the vsen struct */
+	vsen = kzalloc(sizeof(*vsen), GFP_KERNEL);
+	if (!vsen)
+		return ERR_PTR(-ENOMEM);
+
+	/* Allocate the pads */
+	vsen->ved.pads = vimc_pads_init(num_pads, pads_flag);
+	if (IS_ERR(vsen->ved.pads)) {
+		ret = PTR_ERR(vsen->ved.pads);
+		goto err_free_vsen;
+	}
+
+	/* Fill the vimc_ent_device struct */
+	vsen->ved.destroy = vimc_sen_destroy;
+	vsen->ved.ent = &vsen->sd.entity;
+
+	/* Initialize the subdev */
+	v4l2_subdev_init(&vsen->sd, &vimc_sen_ops);
+	vsen->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
+	vsen->sd.entity.ops = &vimc_sen_mops;
+	vsen->sd.owner = THIS_MODULE;
+	strlcpy(vsen->sd.name, name, sizeof(vsen->sd.name));
+	v4l2_set_subdevdata(&vsen->sd, &vsen->ved);
+
+	/* Expose this subdev to user space */
+	vsen->sd.flags = V4L2_SUBDEV_FL_HAS_DEVNODE;
+
+	/* Initialize the media entity */
+	ret = media_entity_pads_init(&vsen->sd.entity,
+				     num_pads, vsen->ved.pads);
+	if (ret)
+		goto err_clean_pads;
+
+	/* Set the active frame format (this is hardcoded for now) */
+	vsen->mbus_format.width = 640;
+	vsen->mbus_format.height = 480;
+	vsen->mbus_format.code = MEDIA_BUS_FMT_RGB888_1X24;
+	vsen->mbus_format.field = V4L2_FIELD_NONE;
+	vsen->mbus_format.colorspace = V4L2_COLORSPACE_SRGB;
+	vsen->mbus_format.quantization = V4L2_QUANTIZATION_FULL_RANGE;
+	vsen->mbus_format.xfer_func = V4L2_XFER_FUNC_SRGB;
+
+	/* Register the subdev with the v4l2 and the media framework */
+	ret = v4l2_device_register_subdev(v4l2_dev, &vsen->sd);
+	if (ret) {
+		dev_err(vsen->sd.v4l2_dev->dev,
+			"%s: subdev register failed (err=%d)\n",
+			vsen->sd.name, ret);
+		goto err_clean_m_ent;
+	}
+
+	return &vsen->ved;
+
+err_clean_m_ent:
+	media_entity_cleanup(&vsen->sd.entity);
+err_clean_pads:
+	vimc_pads_cleanup(vsen->ved.pads);
+err_free_vsen:
+	kfree(vsen);
+
+	return ERR_PTR(ret);
+}

drivers/media/platform/vimc/vimc-sensor.h

@@ -0,0 +1,28 @@
+/*
+ * vimc-sensor.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _VIMC_SENSOR_H_
+#define _VIMC_SENSOR_H_
+
+#include "vimc-core.h"
+
+struct vimc_ent_device *vimc_sen_create(struct v4l2_device *v4l2_dev,
+					const char *const name,
+					u16 num_pads,
+					const unsigned long *pads_flag);
+
+#endif