libcamera: v4l2_subdevice: Add V4L2Subdevice::Route structure

The V4L2Subdevice class deals with streams in two places:

- In routing tables, streams as expressed as a pad number and a stream
  number in a v4l2_subdev_route instance.
- In the format and selection get and set functions, streams as
  expressed using the Stream structure, which binds the pad number and
  stream number.

Expressing streams in different ways requires pipeline handlers and
other helpers to convert between the two representations. This isn't
much of an issue yet as libcamera has little stream-aware code, but it
is expected to increasingly become a burden.

To simplify the API, introduce a V4L2Subdevice::Route structure that
mimicks the kernel v4l2_subdev_route structure but represents streams as
V4L2Subdevice::Stream instances. This will improve seamless integration
of routes, formats and selection rectangles.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/v4l2_subdevice.h

@@ -95,7 +95,23 @@ public:
 		unsigned int stream;
 	};
 
-	using Routing = std::vector<struct v4l2_subdev_route>;
+	struct Route {
+		Route()
+			: flags(0)
+		{
+		}
+
+		Route(const Stream &snk, const Stream &src, uint32_t f)
+			: sink(snk), source(src), flags(f)
+		{
+		}
+
+		Stream sink;
+		Stream source;
+		uint32_t flags;
+	};
+
+	using Routing = std::vector<Route>;
 
 	explicit V4L2Subdevice(const MediaEntity *entity);
 	~V4L2Subdevice();
@@ -174,6 +190,7 @@ static inline bool operator!=(const V4L2Subdevice::Stream &lhs,
 }
 
 std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Stream &stream);
+std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Route &route);
 std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Routing &routing);
 
 } /* namespace libcamera */

src/libcamera/pipeline/imx8-isi/imx8-isi.cpp

@@ -827,16 +827,10 @@ int PipelineHandlerISI::configure(Camera *camera, CameraConfiguration *c)
 	unsigned int xbarFirstSource = crossbar_->entity()->pads().size() / 2 + 1;
 
 	for (const auto &[idx, config] : utils::enumerate(*c)) {
-		struct v4l2_subdev_route route = {
+		uint32_t sourcePad = xbarFirstSource + idx;
-			.sink_pad = data->xbarSink_,
+		routing.emplace_back(V4L2Subdevice::Stream{ data->xbarSink_, 0 },
-			.sink_stream = 0,
+				     V4L2Subdevice::Stream{ sourcePad, 0 },
-			.source_pad = static_cast<uint32_t>(xbarFirstSource + idx),
+				     V4L2_SUBDEV_ROUTE_FL_ACTIVE);
-			.source_stream = 0,
-			.flags = V4L2_SUBDEV_ROUTE_FL_ACTIVE,
-			.reserved = {}
-		};
-
-		routing.push_back(route);
 	}
 
 	int ret = crossbar_->setRouting(&routing, V4L2Subdevice::ActiveFormat);

src/libcamera/pipeline/simple/simple.cpp

@@ -852,17 +852,17 @@ std::vector<const MediaPad *> SimpleCameraData::routedSourcePads(MediaPad *sink)
 
 	std::vector<const MediaPad *> pads;
 
-	for (const struct v4l2_subdev_route &route : routing) {
+	for (const V4L2Subdevice::Route &route : routing) {
-		if (sink->index() != route.sink_pad ||
+		if (sink->index() != route.sink.pad ||
 		    !(route.flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
 			continue;
 
-		const MediaPad *pad = entity->getPadByIndex(route.source_pad);
+		const MediaPad *pad = entity->getPadByIndex(route.source.pad);
 		if (!pad) {
 			LOG(SimplePipeline, Warning)
 				<< "Entity " << entity->name()
 				<< " has invalid route source pad "
-				<< route.source_pad;
+				<< route.source.pad;
 		}
 
 		pads.push_back(pad);

src/libcamera/v4l2_subdevice.cpp

@@ -898,6 +898,53 @@ std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Stream &stream)
 	return out;
 }
 
+/**
+ * \class V4L2Subdevice::Route
+ * \brief V4L2 subdevice routing table entry
+ *
+ * This class models a route in the subdevice routing table. It is similar to
+ * the v4l2_subdev_route structure, but uses the V4L2Subdevice::Stream class
+ * for easier usage with the V4L2Subdevice stream-aware functions.
+ *
+ * \var V4L2Subdevice::Route::sink
+ * \brief The sink stream of the route
+ *
+ * \var V4L2Subdevice::Route::source
+ * \brief The source stream of the route
+ *
+ * \var V4L2Subdevice::Route::flags
+ * \brief The route flags (V4L2_SUBDEV_ROUTE_FL_*)
+ */
+
+/**
+ * \fn V4L2Subdevice::Route::Route()
+ * \brief Construct a Route with default streams
+ */
+
+/**
+ * \fn V4L2Subdevice::Route::Route(const Stream &sink, const Stream &source,
+ * uint32_t flags)
+ * \brief Construct a Route from \a sink to \a source
+ * \param[in] sink The sink stream
+ * \param[in] source The source stream
+ * \param[in] flags The route flags
+ */
+
+/**
+ * \brief Insert a text representation of a V4L2Subdevice::Route into an
+ * output stream
+ * \param[in] out The output stream
+ * \param[in] route The V4L2Subdevice::Route
+ * \return The output stream \a out
+ */
+std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Route &route)
+{
+	out << route.sink << " -> " << route.source
+	    << " (" << utils::hex(route.flags) << ")";
+
+	return out;
+}
+
 /**
  * \typedef V4L2Subdevice::Routing
  * \brief V4L2 subdevice routing table
@@ -915,10 +962,7 @@ std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Stream &stream)
 std::ostream &operator<<(std::ostream &out, const V4L2Subdevice::Routing &routing)
 {
 	for (const auto &[i, route] : utils::enumerate(routing)) {
-		out << "[" << i << "] "
+		out << "[" << i << "] " << route;
-		    << route.sink_pad << "/" << route.sink_stream << " -> "
-		    << route.source_pad << "/" << route.source_stream
-		    << " (" << utils::hex(route.flags) << ")";
 		if (i != routing.size() - 1)
 			out << ", ";
 	}
@@ -1272,6 +1316,30 @@ int V4L2Subdevice::setFormat(const Stream &stream, V4L2SubdeviceFormat *format,
  * \return 0 on success or a negative error code otherwise
  */
 
+namespace {
+
+void routeFromKernel(V4L2Subdevice::Route &route,
+		     const struct v4l2_subdev_route &kroute)
+{
+	route.sink.pad = kroute.sink_pad;
+	route.sink.stream = kroute.sink_stream;
+	route.source.pad = kroute.source_pad;
+	route.source.stream = kroute.source_stream;
+	route.flags = kroute.flags;
+}
+
+void routeToKernel(const V4L2Subdevice::Route &route,
+		   struct v4l2_subdev_route &kroute)
+{
+	kroute.sink_pad = route.sink.pad;
+	kroute.sink_stream = route.sink.stream;
+	kroute.source_pad = route.source.pad;
+	kroute.source_stream = route.source.stream;
+	kroute.flags = route.flags;
+}
+
+} /* namespace */
+
 /**
  * \brief Retrieve the subdevice's internal routing table
  * \param[out] routing The routing table
@@ -1282,6 +1350,8 @@ int V4L2Subdevice::setFormat(const Stream &stream, V4L2SubdeviceFormat *format,
  */
 int V4L2Subdevice::getRouting(Routing *routing, Whence whence)
 {
+	routing->clear();
+
 	if (!caps_.hasStreams())
 		return 0;
 
@@ -1300,8 +1370,8 @@ int V4L2Subdevice::getRouting(Routing *routing, Whence whence)
 		return ret;
 	}
 
-	routing->resize(rt.num_routes);
+	std::vector<struct v4l2_subdev_route> routes{ rt.num_routes };
-	rt.routes = reinterpret_cast<uintptr_t>(routing->data());
+	rt.routes = reinterpret_cast<uintptr_t>(routes.data());
 
 	ret = ioctl(VIDIOC_SUBDEV_G_ROUTING, &rt);
 	if (ret) {
@@ -1310,11 +1380,16 @@ int V4L2Subdevice::getRouting(Routing *routing, Whence whence)
 		return ret;
 	}
 
-	if (rt.num_routes != routing->size()) {
+	if (rt.num_routes != routes.size()) {
 		LOG(V4L2, Error) << "Invalid number of routes";
 		return -EINVAL;
 	}
 
+	routing->resize(rt.num_routes);
+
+	for (const auto &[i, route] : utils::enumerate(routes))
+		routeFromKernel((*routing)[i], route);
+
 	return 0;
 }
 
@@ -1332,13 +1407,20 @@ int V4L2Subdevice::getRouting(Routing *routing, Whence whence)
  */
 int V4L2Subdevice::setRouting(Routing *routing, Whence whence)
 {
-	if (!caps_.hasStreams())
+	if (!caps_.hasStreams()) {
+		routing->clear();
 		return 0;
+	}
+
+	std::vector<struct v4l2_subdev_route> routes{ routing->size() };
+
+	for (const auto &[i, route] : utils::enumerate(*routing))
+		routeToKernel(route, routes[i]);
 
 	struct v4l2_subdev_routing rt = {};
 	rt.which = whence;
-	rt.num_routes = routing->size();
+	rt.num_routes = routes.size();
-	rt.routes = reinterpret_cast<uintptr_t>(routing->data());
+	rt.routes = reinterpret_cast<uintptr_t>(routes.data());
 
 	int ret = ioctl(VIDIOC_SUBDEV_S_ROUTING, &rt);
 	if (ret) {
@@ -1346,8 +1428,12 @@ int V4L2Subdevice::setRouting(Routing *routing, Whence whence)
 		return ret;
 	}
 
+	routes.resize(rt.num_routes);
 	routing->resize(rt.num_routes);
 
+	for (const auto &[i, route] : utils::enumerate(routes))
+		routeFromKernel((*routing)[i], route);
+
 	return 0;
 }