media: add helpers for memory-to-memory media controller

A memory-to-memory pipeline device consists in three
entities: two DMA engine and one video processing entities.
The DMA engine entities are linked to a V4L interface.

This commit add a new v4l2_m2m_{un}register_media_controller
API to register this topology.

For instance, a typical mem2mem device topology would
look like this:

Device topology
- entity 1: source (1 pad, 1 link)
            type Node subtype V4L flags 0
	pad0: Source
		-> "proc":1 [ENABLED,IMMUTABLE]

- entity 3: proc (2 pads, 2 links)
            type Node subtype Unknown flags 0
	pad0: Source
		-> "sink":0 [ENABLED,IMMUTABLE]
	pad1: Sink
		<- "source":0 [ENABLED,IMMUTABLE]

- entity 6: sink (1 pad, 1 link)
            type Node subtype V4L flags 0
	pad0: Sink
		<- "proc":0 [ENABLED,IMMUTABLE]

[hans.verkuil@cisco.com: mark interface links as IMMUTABLE]

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/v4l2-core/v4l2-dev.c

@@ -202,7 +202,7 @@ static void v4l2_device_release(struct device *cd)
 	mutex_unlock(&videodev_lock);
 
 #if defined(CONFIG_MEDIA_CONTROLLER)
-	if (v4l2_dev->mdev) {
+	if (v4l2_dev->mdev && vdev->vfl_dir != VFL_DIR_M2M) {
 		/* Remove interfaces and interface links */
 		media_devnode_remove(vdev->intf_devnode);
 		if (vdev->entity.function != MEDIA_ENT_F_UNKNOWN)
@@ -733,19 +733,22 @@ static void determine_valid_ioctls(struct video_device *vdev)
 			BASE_VIDIOC_PRIVATE);
 }
 
-static int video_register_media_controller(struct video_device *vdev, int type)
+static int video_register_media_controller(struct video_device *vdev)
 {
 #if defined(CONFIG_MEDIA_CONTROLLER)
 	u32 intf_type;
 	int ret;
 
-	if (!vdev->v4l2_dev->mdev)
+	/* Memory-to-memory devices are more complex and use
+	 * their own function to register its mc entities.
+	 */
+	if (!vdev->v4l2_dev->mdev || vdev->vfl_dir == VFL_DIR_M2M)
 		return 0;
 
 	vdev->entity.obj_type = MEDIA_ENTITY_TYPE_VIDEO_DEVICE;
 	vdev->entity.function = MEDIA_ENT_F_UNKNOWN;
 
-	switch (type) {
+	switch (vdev->vfl_type) {
 	case VFL_TYPE_GRABBER:
 		intf_type = MEDIA_INTF_T_V4L_VIDEO;
 		vdev->entity.function = MEDIA_ENT_F_IO_V4L;
@@ -994,7 +997,7 @@ int __video_register_device(struct video_device *vdev,
 	v4l2_device_get(vdev->v4l2_dev);
 
 	/* Part 5: Register the entity. */
-	ret = video_register_media_controller(vdev, type);
+	ret = video_register_media_controller(vdev);
 
 	/* Part 6: Activate this minor. The char device can now be used. */
 	set_bit(V4L2_FL_REGISTERED, &vdev->flags);

drivers/media/v4l2-core/v4l2-mem2mem.c

@@ -17,9 +17,11 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 
+#include <media/media-device.h>
 #include <media/videobuf2-v4l2.h>
 #include <media/v4l2-mem2mem.h>
 #include <media/v4l2-dev.h>
+#include <media/v4l2-device.h>
 #include <media/v4l2-fh.h>
 #include <media/v4l2-event.h>
 
@@ -50,6 +52,17 @@ module_param(debug, bool, 0644);
  * offsets but for different queues */
 #define DST_QUEUE_OFF_BASE	(1 << 30)
 
+enum v4l2_m2m_entity_type {
+	MEM2MEM_ENT_TYPE_SOURCE,
+	MEM2MEM_ENT_TYPE_SINK,
+	MEM2MEM_ENT_TYPE_PROC
+};
+
+static const char * const m2m_entity_name[] = {
+	"source",
+	"sink",
+	"proc"
+};
 
 /**
  * struct v4l2_m2m_dev - per-device context
@@ -60,6 +73,15 @@ module_param(debug, bool, 0644);
  */
 struct v4l2_m2m_dev {
 	struct v4l2_m2m_ctx	*curr_ctx;
+#ifdef CONFIG_MEDIA_CONTROLLER
+	struct media_entity	*source;
+	struct media_pad	source_pad;
+	struct media_entity	sink;
+	struct media_pad	sink_pad;
+	struct media_entity	proc;
+	struct media_pad	proc_pads[2];
+	struct media_intf_devnode *intf_devnode;
+#endif
 
 	struct list_head	job_queue;
 	spinlock_t		job_spinlock;
@@ -594,6 +616,174 @@ int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 }
 EXPORT_SYMBOL(v4l2_m2m_mmap);
 
+#if defined(CONFIG_MEDIA_CONTROLLER)
+void v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev)
+{
+	media_remove_intf_links(&m2m_dev->intf_devnode->intf);
+	media_devnode_remove(m2m_dev->intf_devnode);
+
+	media_entity_remove_links(m2m_dev->source);
+	media_entity_remove_links(&m2m_dev->sink);
+	media_entity_remove_links(&m2m_dev->proc);
+	media_device_unregister_entity(m2m_dev->source);
+	media_device_unregister_entity(&m2m_dev->sink);
+	media_device_unregister_entity(&m2m_dev->proc);
+	kfree(m2m_dev->source->name);
+	kfree(m2m_dev->sink.name);
+	kfree(m2m_dev->proc.name);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_unregister_media_controller);
+
+static int v4l2_m2m_register_entity(struct media_device *mdev,
+	struct v4l2_m2m_dev *m2m_dev, enum v4l2_m2m_entity_type type,
+	struct video_device *vdev, int function)
+{
+	struct media_entity *entity;
+	struct media_pad *pads;
+	char *name;
+	unsigned int len;
+	int num_pads;
+	int ret;
+
+	switch (type) {
+	case MEM2MEM_ENT_TYPE_SOURCE:
+		entity = m2m_dev->source;
+		pads = &m2m_dev->source_pad;
+		pads[0].flags = MEDIA_PAD_FL_SOURCE;
+		num_pads = 1;
+		break;
+	case MEM2MEM_ENT_TYPE_SINK:
+		entity = &m2m_dev->sink;
+		pads = &m2m_dev->sink_pad;
+		pads[0].flags = MEDIA_PAD_FL_SINK;
+		num_pads = 1;
+		break;
+	case MEM2MEM_ENT_TYPE_PROC:
+		entity = &m2m_dev->proc;
+		pads = m2m_dev->proc_pads;
+		pads[0].flags = MEDIA_PAD_FL_SINK;
+		pads[1].flags = MEDIA_PAD_FL_SOURCE;
+		num_pads = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	entity->obj_type = MEDIA_ENTITY_TYPE_BASE;
+	if (type != MEM2MEM_ENT_TYPE_PROC) {
+		entity->info.dev.major = VIDEO_MAJOR;
+		entity->info.dev.minor = vdev->minor;
+	}
+	len = strlen(vdev->name) + 2 + strlen(m2m_entity_name[type]);
+	name = kmalloc(len, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+	snprintf(name, len, "%s-%s", vdev->name, m2m_entity_name[type]);
+	entity->name = name;
+	entity->function = function;
+
+	ret = media_entity_pads_init(entity, num_pads, pads);
+	if (ret)
+		return ret;
+	ret = media_device_register_entity(mdev, entity);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+int v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
+		struct video_device *vdev, int function)
+{
+	struct media_device *mdev = vdev->v4l2_dev->mdev;
+	struct media_link *link;
+	int ret;
+
+	if (!mdev)
+		return 0;
+
+	/* A memory-to-memory device consists in two
+	 * DMA engine and one video processing entities.
+	 * The DMA engine entities are linked to a V4L interface
+	 */
+
+	/* Create the three entities with their pads */
+	m2m_dev->source = &vdev->entity;
+	ret = v4l2_m2m_register_entity(mdev, m2m_dev,
+			MEM2MEM_ENT_TYPE_SOURCE, vdev, MEDIA_ENT_F_IO_V4L);
+	if (ret)
+		return ret;
+	ret = v4l2_m2m_register_entity(mdev, m2m_dev,
+			MEM2MEM_ENT_TYPE_PROC, vdev, function);
+	if (ret)
+		goto err_rel_entity0;
+	ret = v4l2_m2m_register_entity(mdev, m2m_dev,
+			MEM2MEM_ENT_TYPE_SINK, vdev, MEDIA_ENT_F_IO_V4L);
+	if (ret)
+		goto err_rel_entity1;
+
+	/* Connect the three entities */
+	ret = media_create_pad_link(m2m_dev->source, 0, &m2m_dev->proc, 1,
+			MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
+	if (ret)
+		goto err_rel_entity2;
+
+	ret = media_create_pad_link(&m2m_dev->proc, 0, &m2m_dev->sink, 0,
+			MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
+	if (ret)
+		goto err_rm_links0;
+
+	/* Create video interface */
+	m2m_dev->intf_devnode = media_devnode_create(mdev,
+			MEDIA_INTF_T_V4L_VIDEO, 0,
+			VIDEO_MAJOR, vdev->minor);
+	if (!m2m_dev->intf_devnode) {
+		ret = -ENOMEM;
+		goto err_rm_links1;
+	}
+
+	/* Connect the two DMA engines to the interface */
+	link = media_create_intf_link(m2m_dev->source,
+			&m2m_dev->intf_devnode->intf,
+			MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
+	if (!link) {
+		ret = -ENOMEM;
+		goto err_rm_devnode;
+	}
+
+	link = media_create_intf_link(&m2m_dev->sink,
+			&m2m_dev->intf_devnode->intf,
+			MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
+	if (!link) {
+		ret = -ENOMEM;
+		goto err_rm_intf_link;
+	}
+	return 0;
+
+err_rm_intf_link:
+	media_remove_intf_links(&m2m_dev->intf_devnode->intf);
+err_rm_devnode:
+	media_devnode_remove(m2m_dev->intf_devnode);
+err_rm_links1:
+	media_entity_remove_links(&m2m_dev->sink);
+err_rm_links0:
+	media_entity_remove_links(&m2m_dev->proc);
+	media_entity_remove_links(m2m_dev->source);
+err_rel_entity2:
+	media_device_unregister_entity(&m2m_dev->proc);
+	kfree(m2m_dev->proc.name);
+err_rel_entity1:
+	media_device_unregister_entity(&m2m_dev->sink);
+	kfree(m2m_dev->sink.name);
+err_rel_entity0:
+	media_device_unregister_entity(m2m_dev->source);
+	kfree(m2m_dev->source->name);
+	return ret;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_register_media_controller);
+#endif
+
 struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops)
 {
 	struct v4l2_m2m_dev *m2m_dev;

include/media/v4l2-mem2mem.h

@@ -47,6 +47,7 @@ struct v4l2_m2m_ops {
 	void (*job_abort)(void *priv);
 };
 
+struct video_device;
 struct v4l2_m2m_dev;
 
 /**
@@ -322,6 +323,24 @@ int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
  */
 struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops);
 
+#if defined(CONFIG_MEDIA_CONTROLLER)
+void v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev);
+int v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
+			struct video_device *vdev, int function);
+#else
+static inline void
+v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev)
+{
+}
+
+static inline int
+v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
+		struct video_device *vdev, int function)
+{
+	return 0;
+}
+#endif
+
 /**
  * v4l2_m2m_release() - cleans up and frees a m2m_dev structure
  *