libcamera: media_device: Create entities with major and minor numbers

Extend the MediaEntity object with device node major and minor numbers,
and retrieve them from the media graph using interfaces. They will be
used by the DeviceEnumerator to retrieve the devnode path.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/media_device.cpp

@@ -208,6 +208,7 @@ int MediaDevice::populate()
 	struct media_v2_entity *ents = nullptr;
 	struct media_v2_link *links = nullptr;
 	struct media_v2_pad *pads = nullptr;
+	struct media_v2_interface *interfaces = nullptr;
 	__u64 version = -1;
 	int ret;
 
@@ -221,6 +222,7 @@ int MediaDevice::populate()
 		topology.ptr_entities = reinterpret_cast<__u64>(ents);
 		topology.ptr_links = reinterpret_cast<__u64>(links);
 		topology.ptr_pads = reinterpret_cast<__u64>(pads);
+		topology.ptr_interfaces = reinterpret_cast<__u64>(interfaces);
 
 		ret = ioctl(fd_, MEDIA_IOC_G_TOPOLOGY, &topology);
 		if (ret < 0) {
@@ -236,10 +238,12 @@ int MediaDevice::populate()
 		delete[] links;
 		delete[] ents;
 		delete[] pads;
+		delete[] interfaces;
 
 		ents = new media_v2_entity[topology.num_entities];
 		links = new media_v2_link[topology.num_links];
 		pads = new media_v2_pad[topology.num_pads];
+		interfaces = new media_v2_interface[topology.num_interfaces];
 
 		version = topology.topology_version;
 	}
@@ -253,6 +257,7 @@ int MediaDevice::populate()
 	delete[] links;
 	delete[] ents;
 	delete[] pads;
+	delete[] interfaces;
 
 	if (!valid_) {
 		clear();
@@ -367,6 +372,46 @@ void MediaDevice::clear()
  * \brief Global list of media entities in the media graph
  */
 
+/**
+ * \brief Find the interface associated with an entity
+ * \param topology The media topology as returned by MEDIA_IOC_G_TOPOLOGY
+ * \param entityId The entity id
+ * \return A pointer to the interface if found, or nullptr otherwise
+ */
+struct media_v2_interface *MediaDevice::findInterface(const struct media_v2_topology &topology,
+			       unsigned int entityId)
+{
+	struct media_v2_link *links = reinterpret_cast<struct media_v2_link *>
+						(topology.ptr_links);
+	unsigned int ifaceId = -1;
+
+	for (unsigned int i = 0; i < topology.num_links; ++i) {
+		/* Search for the interface to entity link. */
+		if (links[i].sink_id != entityId)
+			continue;
+
+		if ((links[i].flags & MEDIA_LNK_FL_LINK_TYPE) !=
+		    MEDIA_LNK_FL_INTERFACE_LINK)
+			continue;
+
+		ifaceId = links[i].source_id;
+		break;
+	}
+
+	if (ifaceId == static_cast<unsigned int>(-1))
+		return nullptr;
+
+	struct media_v2_interface *ifaces = reinterpret_cast<struct media_v2_interface *>
+						(topology.ptr_interfaces);
+
+	for (unsigned int i = 0; i < topology.num_interfaces; ++i) {
+		if (ifaces[i].id == ifaceId)
+			return &ifaces[i];
+	}
+
+	return nullptr;
+}
+
 /*
  * For each entity in the media graph create a MediaEntity and store a
  * reference in the media device objects map and entities list.
@@ -377,7 +422,21 @@ bool MediaDevice::populateEntities(const struct media_v2_topology &topology)
 					 (topology.ptr_entities);
 
 	for (unsigned int i = 0; i < topology.num_entities; ++i) {
-		MediaEntity *entity = new MediaEntity(&mediaEntities[i]);
+		/*
+		 * Find the interface linked to this entity to get the device
+		 * node major and minor numbers.
+		 */
+		struct media_v2_interface *iface =
+			findInterface(topology, mediaEntities[i].id);
+
+		MediaEntity *entity;
+		if (iface)
+			entity = new MediaEntity(&mediaEntities[i],
+						 iface->devnode.major,
+						 iface->devnode.minor);
+		else
+			entity = new MediaEntity(&mediaEntities[i]);
+
 		if (!addObject(entity)) {
 			delete entity;
 			return false;