[media] media-device: export the entity function via new ioctl

Now that entities have a main function, expose it via
MEDIA_IOC_G_TOPOLOGY ioctl.

Please notice that some entities may have secundary functions.
Such use case will be addressed later, when we add support for the
Media Controller properties.
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/media-device.c

@@ -263,6 +263,7 @@ static long __media_device_get_topology(struct media_device *mdev,
 		/* Copy fields to userspace struct if not error */
 		memset(&uentity, 0, sizeof(uentity));
 		uentity.id = entity->graph_obj.id;
+		uentity.function = entity->function;
 		strncpy(uentity.name, entity->name,
 			sizeof(uentity.name));
 

include/uapi/linux/media.h

@@ -276,7 +276,8 @@ struct media_links_enum {
 struct media_v2_entity {
 	__u32 id;
 	char name[64];		/* FIXME: move to a property? (RFC says so) */
-	__u16 reserved[14];
+	__u32 function;		/* Main function of the entity */
+	__u16 reserved[12];
 };
 
 /* Should match the specific fields at media_intf_devnode */