Re: [PATCH v7] [media] vimc: Virtual Media Controller core, capture and sensor

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On 2017-03-25 02:11 PM, Helen Koike wrote:
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@xxxxxxxxxxxxx>

---

Patch based in media/master tree, and available here:
https://github.com/helen-fornazier/opw-staging/tree/vimc/devel/v7

Changes since v6:
- add kernel-docs in vimc-core.h
- reorder list_del call in vimc_cap_return_all_buffers()
- call media_pipeline_stop in vimc_cap_start_streaming when fail
- remove DMA comment (left over from the sample driver)
- remove vb2_set_plane_payload call in vimc_cap_buffer_prepare
- remove format verification in vimc_cap_link_validate
- set vimc_pix_map_list as static
- use MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN in vimc_raw_create()
- register media device after creating the topology and unregister it
before destroying the topology
- replace devm_kzalloc by kzalloc for allocating struct vimc_device
- uset TASK_UNINTERRUPTIBLE for vimc_thread_sen
- do not allow the creation of a sensor with no pads
- add more verbose description in Kconfig
- change copyright to 2017
- arrange includes: number before letters
- remove v4l2_dev pointer from vimc_cap_device structure
- coding style adjustments
- remove entity variable in vimc_cap_pipeline_s_stream
- declare and assign variables in vimc_cap_link_validate
- declare vimc_dev_release() and vimc_pdev closer to vimc_init()
- remove pad check in vimc_sen_enum_{mbus_code,frame_size} that is
already performed by v4l2-subdev.c
- fix multiline comments to start with /*
- reorder variable declaration in functions
- remove pad and subdevice type check in vimc_cap_pipeline_s_stream
- add a note that sensor nodes can can have more then one source pad
- remove the use of entity->use_count in the core and attach the ved
structure in sd or vd, use
  ent->obj_type to know which structure (sd or vd) to use
- rename vdev (video_device) to vd to be similar to sd (subdev)

Changes since v5:
- Fix message "Entity type for entity Sensor A was not initialized!"
  by initializing the sensor entity.function after the calling
  v4l2_subded_init
- populate device_caps in vimc_cap_create instead of in
  vimc_cap_querycap
- Fix typo in vimc-core.c s/de/the

Changes since v4:
- coding style fixes
- remove BUG_ON
- change copyright to 2016
- depens on VIDEO_V4L2_SUBDEV_API instead of select
- remove assignement of V4L2_CAP_DEVICE_CAPS
- s/vimc_cap_g_fmt_vid_cap/vimc_cap_fmt_vid_cap
- fix vimc_cap_queue_setup declaration type
- remove wrong buffer size check and add it in vimc_cap_buffer_prepare
- vimc_cap_create: remove unecessary check if v4l2_dev or
v4l2_dev->dev is null
- vimc_cap_create: only allow a single pad
- vimc_sen_create: only allow source pads, remove unecessary source pads
checks in vimc_thread_sen

Changes since v3: fix rmmod crash and built-in compile
- Re-order unregister calls in vimc_device_unregister function (remove
rmmod issue)
- Call media_device_unregister_entity in vimc_raw_destroy
- Add depends on VIDEO_DEV && VIDEO_V4L2 and select VIDEOBUF2_VMALLOC
- Check *nplanes in queue_setup (this remove v4l2-compliance fail)
- Include <linux/kthread.h> in vimc-sensor.c
- Move include of <linux/slab.h> from vimc-core.c to vimc-core.h
- Generate 60 frames per sec instead of 1 in the sensor

Changes since v2: update with current media master tree
- Add struct media_pipeline in vimc_cap_device
- Use vb2_v4l2_buffer instead of vb2_buffer
- Typos
- Remove usage of entity->type and use entity->function instead
- Remove fmt argument from queue setup
- Use ktime_get_ns instead of v4l2_get_timestamp
- Iterate over link's list using list_for_each_entry
- Use media_device_{init, cleanup}
- Use entity->use_count to keep track of entities instead of the old
entity->id
- Replace media_entity_init by media_entity_pads_init
---
 drivers/media/platform/Kconfig             |   2 +
 drivers/media/platform/Makefile            |   1 +
 drivers/media/platform/vimc/Kconfig        |  14 +
 drivers/media/platform/vimc/Makefile       |   3 +
 drivers/media/platform/vimc/vimc-capture.c | 536 ++++++++++++++++++++++
 drivers/media/platform/vimc/vimc-capture.h |  28 ++
 drivers/media/platform/vimc/vimc-core.c    | 696
+++++++++++++++++++++++++++++
 drivers/media/platform/vimc/vimc-core.h    | 123 +++++
 drivers/media/platform/vimc/vimc-sensor.c  | 279 ++++++++++++
 drivers/media/platform/vimc/vimc-sensor.h  |  28 ++
 10 files changed, 1710 insertions(+)
 create mode 100644 drivers/media/platform/vimc/Kconfig
 create mode 100644 drivers/media/platform/vimc/Makefile
 create mode 100644 drivers/media/platform/vimc/vimc-capture.c
 create mode 100644 drivers/media/platform/vimc/vimc-capture.h
 create mode 100644 drivers/media/platform/vimc/vimc-core.c
 create mode 100644 drivers/media/platform/vimc/vimc-core.h
 create mode 100644 drivers/media/platform/vimc/vimc-sensor.c
 create mode 100644 drivers/media/platform/vimc/vimc-sensor.h

diff --git a/drivers/media/platform/Kconfig
b/drivers/media/platform/Kconfig
index 53f6f12..6dab7e6 100644
--- a/drivers/media/platform/Kconfig
+++ b/drivers/media/platform/Kconfig
@@ -466,6 +466,8 @@ menuconfig V4L_TEST_DRIVERS

 if V4L_TEST_DRIVERS

+source "drivers/media/platform/vimc/Kconfig"
+
 source "drivers/media/platform/vivid/Kconfig"

 config VIDEO_VIM2M
diff --git a/drivers/media/platform/Makefile
b/drivers/media/platform/Makefile
index 8959f6e..4af4cce 100644
--- a/drivers/media/platform/Makefile
+++ b/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

diff --git a/drivers/media/platform/vimc/Kconfig
b/drivers/media/platform/vimc/Kconfig
new file mode 100644
index 0000000..dd285fa
--- /dev/null
+++ b/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 drivers 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.
diff --git a/drivers/media/platform/vimc/Makefile
b/drivers/media/platform/vimc/Makefile
new file mode 100644
index 0000000..c45195e
--- /dev/null
+++ b/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
diff --git a/drivers/media/platform/vimc/vimc-capture.c
b/drivers/media/platform/vimc/vimc-capture.c
new file mode 100644
index 0000000..8f77fc8
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-capture.c
@@ -0,0 +1,536 @@
+/*
+ * vimc-capture.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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 vd;
+    struct device *dev;
+    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->vd.v4l2_dev->name);
+
+    return 0;
+}
+
+static int vimc_cap_enum_input(struct file *file, void *priv,
+                   struct v4l2_input *i)
+{
+    /* We only have one input */
+    if (i->index > 0)
+        return -EINVAL;
+
+    i->type = V4L2_INPUT_TYPE_CAMERA;
+    strlcpy(i->name, "VIMC capture", sizeof(i->name));
+
+    return 0;
+}
+
+static int vimc_cap_g_input(struct file *file, void *priv, unsigned
int *i)
+{
+    /* We only have one input */
+    *i = 0;
+    return 0;
+}
+
+static int vimc_cap_s_input(struct file *file, void *priv, unsigned
int i)
+{
+    /* We only have one input */
+    return i ? -EINVAL : 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_enum_input = vimc_cap_enum_input,
+    .vidioc_g_input = vimc_cap_g_input,
+    .vidioc_s_input = vimc_cap_s_input,
+
+    .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_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->vd.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->vd.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->vd.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->dev, "buffer too small (%lu < %lu)\n",
+            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,
+                            vd.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->dev,
+        "cap: %s: link validate formats src:%dx%d %d sink:%dx%d %d\n",
+        vcap->vd.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 -EINVAL;
+
+    /*
+     * 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 -EINVAL;
+
+    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->vd);
+    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;
+
+    /* If the stream in this node is not active, just return */
+    mutex_lock(&vcap->lock);
+    if (!vb2_is_busy(&vcap->queue)) {
+        mutex_unlock(&vcap->lock);
+        return;
+    }
+    mutex_unlock(&vcap->lock);
+
+    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 *vd;
+    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);
+
+    /* Link the vimc_cap_device struct with dev parent */
+    vcap->dev = v4l2_dev->dev;
+
+    /* 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->vd.entity.name = name;
+    vcap->vd.entity.function = MEDIA_ENT_F_IO_V4L;
+    ret = media_entity_pads_init(&vcap->vd.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->dev,
+            "vb2 queue init failed (err=%d)\n", 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->vd.entity;
+    vcap->ved.process_frame = vimc_cap_process_frame;
+
+    /* Initialize the video_device struct */
+    vd = &vcap->vd;
+    vd->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
+    vd->entity.ops = &vimc_cap_mops;
+    vd->release = video_device_release_empty;
+    vd->fops = &vimc_cap_fops;
+    vd->ioctl_ops = &vimc_cap_ioctl_ops;
+    vd->lock = &vcap->lock;
+    vd->queue = q;
+    vd->v4l2_dev = v4l2_dev;
+    vd->vfl_dir = VFL_DIR_RX;
+    strlcpy(vd->name, name, sizeof(vd->name));
+    video_set_drvdata(vd, &vcap->ved);
+
+    /* Register the video_device with the v4l2 and the media framework */
+    ret = video_register_device(vd, VFL_TYPE_GRABBER, -1);
+    if (ret) {
+        dev_err(vcap->dev,
+            "video register failed (err=%d)\n", ret);
+        goto err_release_queue;
+    }
+
+    return &vcap->ved;
+
+err_release_queue:
+    vb2_queue_release(q);
+err_clean_m_ent:
+    media_entity_cleanup(&vcap->vd.entity);
+err_clean_pads:
+    vimc_pads_cleanup(vcap->ved.pads);
+err_free_vcap:
+    kfree(vcap);
+
+    return ERR_PTR(ret);
+}
diff --git a/drivers/media/platform/vimc/vimc-capture.h
b/drivers/media/platform/vimc/vimc-capture.h
new file mode 100644
index 0000000..c7e633d
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-capture.h
@@ -0,0 +1,28 @@
+/*
+ * vimc-capture.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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
diff --git a/drivers/media/platform/vimc/vimc-core.c
b/drivers/media/platform/vimc/vimc-core.c
new file mode 100644
index 0000000..2dc2ca8
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-core.c
@@ -0,0 +1,696 @@
+/*
+ * vimc-core.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <media/media-device.h>
+#include <media/v4l2-device.h>
+
+#include "vimc-capture.h"
+#include "vimc-core.h"
+#include "vimc-sensor.h"
+
+#define VIMC_PDEV_NAME "vimc"
+#define VIMC_MDEV_MODEL_NAME "VIMC MDEV"
+
+#define VIMC_ENT_LINK(src, srcpad, sink, sinkpad, link_flags) {    \
+    .src_ent = src,                        \
+    .src_pad = srcpad,                    \
+    .sink_ent = sink,                    \
+    .sink_pad = sinkpad,                    \
+    .flags = link_flags,                    \
+}
+
+struct vimc_device {
+    /*
+     * The pipeline configuration
+     * (filled before calling vimc_device_register)
+     */
+    const struct vimc_pipeline_config *pipe_cfg;
+
+    /* The Associated media_device parent */
+    struct media_device mdev;
+
+    /* Internal v4l2 parent device*/
+    struct v4l2_device v4l2_dev;
+
+    /* Internal topology */
+    struct vimc_ent_device **ved;
+};
+
+/**
+ * enum vimc_ent_node - Select the functionality of a node in the
topology
+ * @VIMC_ENT_NODE_SENSOR:    A node of type SENSOR simulates a camera
sensor
+ *                generating internal images in bayer format and
+ *                propagating those images through the pipeline
+ * @VIMC_ENT_NODE_CAPTURE:    A node of type CAPTURE is a v4l2
video_device
+ *                that exposes the received image from the
+ *                pipeline to the user space
+ * @VIMC_ENT_NODE_INPUT:    A node of type INPUT is a v4l2
video_device that
+ *                receives images from the user space and
+ *                propagates them through the pipeline
+ * @VIMC_ENT_NODE_DEBAYER:    A node type DEBAYER expects to receive
a frame
+ *                in bayer format converts it to RGB
+ * @VIMC_ENT_NODE_SCALER:    A node of type SCALER scales the
received image
+ *                by a given multiplier
+ *
+ * This enum is used in the entity configuration struct to allow the
definition
+ * of a custom topology specifying the role of each node on it.
+ */
+enum vimc_ent_node {
+    VIMC_ENT_NODE_SENSOR,
+    VIMC_ENT_NODE_CAPTURE,
+    VIMC_ENT_NODE_INPUT,
+    VIMC_ENT_NODE_DEBAYER,
+    VIMC_ENT_NODE_SCALER,
+};
+
+/* Structure which describes individual configuration for each entity */
+struct vimc_ent_config {
+    const char *name;
+    size_t pads_qty;
+    const unsigned long *pads_flag;
+    enum vimc_ent_node node;
+};
+
+/* Structure which describes links between entities */
+struct vimc_ent_link {
+    unsigned int src_ent;
+    u16 src_pad;
+    unsigned int sink_ent;
+    u16 sink_pad;
+    u32 flags;
+};
+
+/* Structure which describes the whole topology */
+struct vimc_pipeline_config {
+    const struct vimc_ent_config *ents;
+    size_t num_ents;
+    const struct vimc_ent_link *links;
+    size_t num_links;
+};
+
+/*
--------------------------------------------------------------------------
+ * Topology Configuration
+ */
+
+static const struct vimc_ent_config ent_config[] = {
+    {
+        .name = "Sensor A",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_SENSOR,
+    },
+    {
+        .name = "Sensor B",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_SENSOR,
+    },
+    {
+        .name = "Debayer A",
+        .pads_qty = 2,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK,
+                             MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_DEBAYER,
+    },
+    {
+        .name = "Debayer B",
+        .pads_qty = 2,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK,
+                             MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_DEBAYER,
+    },
+    {
+        .name = "Raw Capture 0",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK},
+        .node = VIMC_ENT_NODE_CAPTURE,
+    },
+    {
+        .name = "Raw Capture 1",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK},
+        .node = VIMC_ENT_NODE_CAPTURE,
+    },
+    {
+        .name = "RGB/YUV Input",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_INPUT,
+    },
+    {
+        .name = "Scaler",
+        .pads_qty = 2,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK,
+                             MEDIA_PAD_FL_SOURCE},
+        .node = VIMC_ENT_NODE_SCALER,
+    },
+    {
+        .name = "RGB/YUV Capture",
+        .pads_qty = 1,
+        .pads_flag = (const unsigned long[]){MEDIA_PAD_FL_SINK},
+        .node = VIMC_ENT_NODE_CAPTURE,
+    },
+};
+
+static const struct vimc_ent_link ent_links[] = {
+    /* Link: Sensor A (Pad 0)->(Pad 0) Debayer A */
+    VIMC_ENT_LINK(0, 0, 2, 0, MEDIA_LNK_FL_ENABLED |
MEDIA_LNK_FL_IMMUTABLE),
+    /* Link: Sensor A (Pad 0)->(Pad 0) Raw Capture 0 */
+    VIMC_ENT_LINK(0, 0, 4, 0, MEDIA_LNK_FL_ENABLED |
MEDIA_LNK_FL_IMMUTABLE),
+    /* Link: Sensor B (Pad 0)->(Pad 0) Debayer B */
+    VIMC_ENT_LINK(1, 0, 3, 0, MEDIA_LNK_FL_ENABLED |
MEDIA_LNK_FL_IMMUTABLE),
+    /* Link: Sensor B (Pad 0)->(Pad 0) Raw Capture 1 */
+    VIMC_ENT_LINK(1, 0, 5, 0, MEDIA_LNK_FL_ENABLED |
MEDIA_LNK_FL_IMMUTABLE),
+    /* Link: Debayer A (Pad 1)->(Pad 0) Scaler */
+    VIMC_ENT_LINK(2, 1, 7, 0, MEDIA_LNK_FL_ENABLED),
+    /* Link: Debayer B (Pad 1)->(Pad 0) Scaler */
+    VIMC_ENT_LINK(3, 1, 7, 0, 0),
+    /* Link: RGB/YUV Input (Pad 0)->(Pad 0) Scaler */
+    VIMC_ENT_LINK(6, 0, 7, 0, 0),
+    /* Link: Scaler (Pad 1)->(Pad 0) RGB/YUV Capture */
+    VIMC_ENT_LINK(7, 1, 8, 0, MEDIA_LNK_FL_ENABLED |
MEDIA_LNK_FL_IMMUTABLE),
+};
+
+static const struct vimc_pipeline_config pipe_cfg = {
+    .ents        = ent_config,
+    .num_ents    = ARRAY_SIZE(ent_config),
+    .links        = ent_links,
+    .num_links    = ARRAY_SIZE(ent_links)
+};
+
+/*
--------------------------------------------------------------------------
*/
+
+static const struct vimc_pix_map vimc_pix_map_list[] = {
+    /* TODO: add all missing formats */
+
+    /* RGB formats */
+    {
+        .code = MEDIA_BUS_FMT_BGR888_1X24,
+        .pixelformat = V4L2_PIX_FMT_BGR24,
+        .bpp = 3,
+    },
+    {
+        .code = MEDIA_BUS_FMT_RGB888_1X24,
+        .pixelformat = V4L2_PIX_FMT_RGB24,
+        .bpp = 3,
+    },
+    {
+        .code = MEDIA_BUS_FMT_ARGB8888_1X32,
+        .pixelformat = V4L2_PIX_FMT_ARGB32,
+        .bpp = 4,
+    },
+
+    /* Bayer formats */
+    {
+        .code = MEDIA_BUS_FMT_SBGGR8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SBGGR8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGBRG8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGBRG8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGRBG8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGRBG8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SRGGB8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SRGGB8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SBGGR10_1X10,
+        .pixelformat = V4L2_PIX_FMT_SBGGR10,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGBRG10_1X10,
+        .pixelformat = V4L2_PIX_FMT_SGBRG10,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGRBG10_1X10,
+        .pixelformat = V4L2_PIX_FMT_SGRBG10,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SRGGB10_1X10,
+        .pixelformat = V4L2_PIX_FMT_SRGGB10,
+        .bpp = 2,
+    },
+
+    /* 10bit raw bayer a-law compressed to 8 bits */
+    {
+        .code = MEDIA_BUS_FMT_SBGGR10_ALAW8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SBGGR10ALAW8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGBRG10_ALAW8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGBRG10ALAW8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGRBG10_ALAW8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGRBG10ALAW8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SRGGB10_ALAW8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SRGGB10ALAW8,
+        .bpp = 1,
+    },
+
+    /* 10bit raw bayer DPCM compressed to 8 bits */
+    {
+        .code = MEDIA_BUS_FMT_SBGGR10_DPCM8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SBGGR10DPCM8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGBRG10_DPCM8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGBRG10DPCM8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGRBG10_DPCM8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SGRBG10DPCM8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SRGGB10_DPCM8_1X8,
+        .pixelformat = V4L2_PIX_FMT_SRGGB10DPCM8,
+        .bpp = 1,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SBGGR12_1X12,
+        .pixelformat = V4L2_PIX_FMT_SBGGR12,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGBRG12_1X12,
+        .pixelformat = V4L2_PIX_FMT_SGBRG12,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SGRBG12_1X12,
+        .pixelformat = V4L2_PIX_FMT_SGRBG12,
+        .bpp = 2,
+    },
+    {
+        .code = MEDIA_BUS_FMT_SRGGB12_1X12,
+        .pixelformat = V4L2_PIX_FMT_SRGGB12,
+        .bpp = 2,
+    },
+};
+
+const struct vimc_pix_map *vimc_pix_map_by_code(u32 code)
+{
+    unsigned int i;
+
+    for (i = 0; i < ARRAY_SIZE(vimc_pix_map_list); i++) {
+        if (vimc_pix_map_list[i].code == code)
+            return &vimc_pix_map_list[i];
+    }
+    return NULL;
+}
+
+const struct vimc_pix_map *vimc_pix_map_by_pixelformat(u32 pixelformat)
+{
+    unsigned int i;
+
+    for (i = 0; i < ARRAY_SIZE(vimc_pix_map_list); i++) {
+        if (vimc_pix_map_list[i].pixelformat == pixelformat)
+            return &vimc_pix_map_list[i];
+    }
+    return NULL;
+}
+
+int vimc_propagate_frame(struct device *dev,
+             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 *vd =
+                    container_of(entity,
+                             struct video_device,
+                             entity);
+                ved = video_get_drvdata(vd);
+            }
+            if (ved && ved->process_frame)
+                ved->process_frame(ved, link->sink, frame);
+        }
+    }
+
+    return 0;
+}
+
+static void vimc_device_unregister(struct vimc_device *vimc)
+{
+    unsigned int i;
+
+    media_device_unregister(&vimc->mdev);
+    /* Cleanup (only initialized) entities */
+    for (i = 0; i < vimc->pipe_cfg->num_ents; i++) {
+        if (vimc->ved[i] && vimc->ved[i]->destroy)
+            vimc->ved[i]->destroy(vimc->ved[i]);
+
+        vimc->ved[i] = NULL;
+    }
+    v4l2_device_unregister(&vimc->v4l2_dev);
+    media_device_cleanup(&vimc->mdev);
+}
+
+/* Helper function to allocate and initialize pads */
+struct media_pad *vimc_pads_init(u16 num_pads, const unsigned long
*pads_flag)
+{
+    struct media_pad *pads;
+    unsigned int i;
+
+    /* Allocate memory for the pads */
+    pads = kcalloc(num_pads, sizeof(*pads), GFP_KERNEL);
+    if (!pads)
+        return ERR_PTR(-ENOMEM);
+
+    /* Initialize the pads */
+    for (i = 0; i < num_pads; i++) {
+        pads[i].index = i;
+        pads[i].flags = pads_flag[i];
+    }
+
+    return pads;
+}
+
+/*
+ * TODO: remove this function when all the
+ * entities specific code are implemented
+ */
+static void vimc_raw_destroy(struct vimc_ent_device *ved)
+{
+    media_device_unregister_entity(ved->ent);
+
+    media_entity_cleanup(ved->ent);
+
+    vimc_pads_cleanup(ved->pads);
+
+    kfree(ved->ent);
+
+    kfree(ved);
+}
+
+/*
+ * TODO: remove this function when all the
+ * entities specific code are implemented
+ */
+static struct vimc_ent_device *vimc_raw_create(struct v4l2_device
*v4l2_dev,
+                           const char *const name,
+                           u16 num_pads,
+                           const unsigned long *pads_flag)
+{
+    struct vimc_ent_device *ved;
+    int ret;
+
+    /* Allocate the main ved struct */
+    ved = kzalloc(sizeof(*ved), GFP_KERNEL);
+    if (!ved)
+        return ERR_PTR(-ENOMEM);
+
+    /* Allocate the media entity */
+    ved->ent = kzalloc(sizeof(*ved->ent), GFP_KERNEL);
+    if (!ved->ent) {
+        ret = -ENOMEM;
+        goto err_free_ved;
+    }
+
+    /* Allocate the pads */
+    ved->pads = vimc_pads_init(num_pads, pads_flag);
+    if (IS_ERR(ved->pads)) {
+        ret = PTR_ERR(ved->pads);
+        goto err_free_ent;
+    }
+
+    /* Initialize the media entity */
+    ved->ent->name = name;
+    ved->ent->function = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
+    ret = media_entity_pads_init(ved->ent, num_pads, ved->pads);
+    if (ret)
+        goto err_cleanup_pads;
+
+    /* Register the media entity */
+    ret = media_device_register_entity(v4l2_dev->mdev, ved->ent);
+    if (ret)
+        goto err_cleanup_entity;
+
+    /* Fill out the destroy function and return */
+    ved->destroy = vimc_raw_destroy;
+    return ved;
+
+err_cleanup_entity:
+    media_entity_cleanup(ved->ent);
+err_cleanup_pads:
+    vimc_pads_cleanup(ved->pads);
+err_free_ent:
+    kfree(ved->ent);
+err_free_ved:
+    kfree(ved);
+
+    return ERR_PTR(ret);
+}
+
+static int vimc_device_register(struct vimc_device *vimc)
+{
+    unsigned int i;
+    int ret;
+
+    /* Allocate memory for the vimc_ent_devices pointers */
+    vimc->ved = devm_kcalloc(vimc->mdev.dev, vimc->pipe_cfg->num_ents,
+                 sizeof(*vimc->ved), GFP_KERNEL);
+    if (!vimc->ved)
+        return -ENOMEM;
+
+    /* Link the media device within the v4l2_device */
+    vimc->v4l2_dev.mdev = &vimc->mdev;
+
+    /* Register the v4l2 struct */
+    ret = v4l2_device_register(vimc->mdev.dev, &vimc->v4l2_dev);
+    if (ret) {
+        dev_err(vimc->mdev.dev,
+            "v4l2 device register failed (err=%d)\n", ret);
+        return ret;
+    }
+
+    /* Initialize entities */
+    for (i = 0; i < vimc->pipe_cfg->num_ents; i++) {
+        struct vimc_ent_device *(*create_func)(struct v4l2_device *,
+                               const char *const,
+                               u16,
+                               const unsigned long *);
+
+        /* Register the specific node */
+        switch (vimc->pipe_cfg->ents[i].node) {
+        case VIMC_ENT_NODE_SENSOR:
+            create_func = vimc_sen_create;
+            break;
+
+        case VIMC_ENT_NODE_CAPTURE:
+            create_func = vimc_cap_create;
+            break;
+
+        /* TODO: Instantiate the specific topology node */
+        case VIMC_ENT_NODE_INPUT:
+        case VIMC_ENT_NODE_DEBAYER:
+        case VIMC_ENT_NODE_SCALER:
+        default:
+            /*
+             * TODO: remove this when all the entities specific
+             * code are implemented
+             */
+            create_func = vimc_raw_create;
+            break;
+        }
+
+        vimc->ved[i] = create_func(&vimc->v4l2_dev,
+                       vimc->pipe_cfg->ents[i].name,
+                       vimc->pipe_cfg->ents[i].pads_qty,
+                       vimc->pipe_cfg->ents[i].pads_flag);
+        if (IS_ERR(vimc->ved[i])) {
+            ret = PTR_ERR(vimc->ved[i]);
+            vimc->ved[i] = NULL;
+            goto err;
+        }
+    }
+
+    /* Initialize the links between entities */
+    for (i = 0; i < vimc->pipe_cfg->num_links; i++) {
+        const struct vimc_ent_link *link = &vimc->pipe_cfg->links[i];
+
+        ret = media_create_pad_link(vimc->ved[link->src_ent]->ent,
+                        link->src_pad,
+                        vimc->ved[link->sink_ent]->ent,
+                        link->sink_pad,
+                        link->flags);
+        if (ret)
+            goto err;
+    }
+
+    /* Register the media device */
+    ret = media_device_register(&vimc->mdev);
+    if (ret) {
+        dev_err(vimc->mdev.dev,
+            "media device register failed (err=%d)\n", ret);
+        return ret;
+    }
+
+    /* Expose all subdev's nodes*/
+    ret = v4l2_device_register_subdev_nodes(&vimc->v4l2_dev);
+    if (ret) {
+        dev_err(vimc->mdev.dev,
+            "vimc subdev nodes registration failed (err=%d)\n",
+            ret);
+        goto err;
+    }
+
+    return 0;
+
+err:
+    /* Destroy the so far created topology */
+    vimc_device_unregister(vimc);
+
+    return ret;
+}
+
+static int vimc_probe(struct platform_device *pdev)
+{
+    struct vimc_device *vimc;
+    int ret;
+
+    /* Prepare the vimc topology structure */
+
+    /* Allocate memory for the vimc structure */
+    vimc = kzalloc(sizeof(*vimc), GFP_KERNEL);
+    if (!vimc)
+        return -ENOMEM;
+
+    /* Set the pipeline configuration struct */
+    vimc->pipe_cfg = &pipe_cfg;
+
+    /* Initialize media device */
+    strlcpy(vimc->mdev.model, VIMC_MDEV_MODEL_NAME,
+        sizeof(vimc->mdev.model));
+    vimc->mdev.dev = &pdev->dev;
+    media_device_init(&vimc->mdev);
+
+    /* Create vimc topology */
+    ret = vimc_device_register(vimc);
+    if (ret) {
+        dev_err(vimc->mdev.dev,
+            "vimc device registration failed (err=%d)\n", ret);
+        kfree(vimc);
+        return ret;
+    }
+
+    /* Link the topology object with the platform device object */
+    platform_set_drvdata(pdev, vimc);
+
+    return 0;
+}
+
+static int vimc_remove(struct platform_device *pdev)
+{
+    struct vimc_device *vimc = platform_get_drvdata(pdev);
+
+    /* Destroy all the topology */
+    vimc_device_unregister(vimc);
+    kfree(vimc);
+
+    return 0;
+}
+
+static void vimc_dev_release(struct device *dev)
+{
+}
+
+static struct platform_device vimc_pdev = {
+    .name        = VIMC_PDEV_NAME,
+    .dev.release    = vimc_dev_release,
+};
+
+static struct platform_driver vimc_pdrv = {
+    .probe        = vimc_probe,
+    .remove        = vimc_remove,
+    .driver        = {
+        .name    = VIMC_PDEV_NAME,
+    },
+};
+
+static int __init vimc_init(void)
+{
+    int ret;
+
+    ret = platform_device_register(&vimc_pdev);
+    if (ret) {
+        dev_err(&vimc_pdev.dev,
+            "platform device registration failed (err=%d)\n", ret);
+        return ret;
+    }
+
+    ret = platform_driver_register(&vimc_pdrv);
+    if (ret) {
+        dev_err(&vimc_pdev.dev,
+            "platform driver registration failed (err=%d)\n", ret);
+
+        platform_device_unregister(&vimc_pdev);
+    }
+
+    return ret;
+}
+
+static void __exit vimc_exit(void)
+{
+    platform_driver_unregister(&vimc_pdrv);
+
+    platform_device_unregister(&vimc_pdev);
+}
+
+module_init(vimc_init);
+module_exit(vimc_exit);
+
+MODULE_DESCRIPTION("Virtual Media Controller Driver (VIMC)");
+MODULE_AUTHOR("Helen Fornazier <helen.fornazier@xxxxxxxxx>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/media/platform/vimc/vimc-core.h
b/drivers/media/platform/vimc/vimc-core.h
new file mode 100644
index 0000000..1d368e9
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-core.h
@@ -0,0 +1,123 @@
+/*
+ * vimc-core.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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
+ * @obj:        the object containing the struct media_entity. It can be
+ *            one of two different types: struct v4l2_subdev
+ *            struct video_device depending of the type of the node.
+ *            The struct vimc_ent_device must be embedded in the obj
+ *            by v4l2_set_subdevdata() or by video_set_drvdata()
+ *
+ * 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);
+    union {
+        struct v4l2_subdev sd;
+        struct video_device vd;
+    } obj;
+};


This union is a left over from a previous implementation test, please disconsider it, I'll
update this in the next version after your comments

diff --git a/drivers/media/platform/vimc/vimc-core.h b/drivers/media/platform/vimc/vimc-core.h
index 1d368e9..4719021 100644
--- a/drivers/media/platform/vimc/vimc-core.h
+++ b/drivers/media/platform/vimc/vimc-core.h
@@ -44,11 +44,6 @@ struct vimc_pix_map {
  * @pads:              the list of pads of the node
  * @destroy:           callback to destroy the node
  * @process_frame:     callback send a frame to that node
- * @obj: the object containing the struct media_entity. It can be
- *                     one of two different types: struct v4l2_subdev
- * struct video_device depending of the type of the node. - * The struct vimc_ent_device must be embedded in the obj
- *                     by v4l2_set_subdevdata() or by video_set_drvdata()
  *
* 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
@@ -64,10 +59,6 @@ struct vimc_ent_device {
        void (*destroy)(struct vimc_ent_device *);
        void (*process_frame)(struct vimc_ent_device *ved,
                              struct media_pad *sink, const void *frame);
-       union {
-               struct v4l2_subdev sd;
-               struct video_device vd;
-       } obj;
 };

 /**


+
+/**
+ * vimc_propagate_frame - propagate a frame through the topology
+ *
+ * @dev:    pointer to struct &device
+ * @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 device *dev,
+             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 - retrieve the vimc_pix_map struct by media 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 - retrieve the 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
diff --git a/drivers/media/platform/vimc/vimc-sensor.c
b/drivers/media/platform/vimc/vimc-sensor.c
new file mode 100644
index 0000000..45892d0
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-sensor.c
@@ -0,0 +1,279 @@
+/*
+ * vimc-sensor.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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 v4l2_device *v4l2_dev;
+    struct device *dev;
+    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);
+
+    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->dev,
+                         &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->v4l2_dev->name);
+        if (IS_ERR(vsen->kthread_sen)) {
+            dev_err(vsen->dev, "kernel_thread() failed\n");
+            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);
+
+    media_entity_cleanup(ved->ent);
+    v4l2_device_unregister_subdev(&vsen->sd);
+    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);
+
+    /* Link the vimc_sen_device struct with the v4l2 parent */
+    vsen->v4l2_dev = v4l2_dev;
+    /* Link the vimc_sen_device struct with the dev parent */
+    vsen->dev = v4l2_dev->dev;
+
+    /* 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;
+    }
+
+    /* Initialize the media entity */
+    vsen->sd.entity.name = name;
+    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;
+
+    /* 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;
+
+    /* Register the subdev with the v4l2 and the media framework */
+    ret = v4l2_device_register_subdev(vsen->v4l2_dev, &vsen->sd);
+    if (ret) {
+        dev_err(vsen->dev,
+            "subdev register failed (err=%d)\n", 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);
+}
diff --git a/drivers/media/platform/vimc/vimc-sensor.h
b/drivers/media/platform/vimc/vimc-sensor.h
new file mode 100644
index 0000000..ef48362
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-sensor.h
@@ -0,0 +1,28 @@
+/*
+ * vimc-sensor.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2017 Helen Koike F. <helen.fornazier@xxxxxxxxx>
+ *
+ * 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






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