[PATCH] pipeline: raspberrypi: Iterate over all Unicam instances in match()

[Naushir Patuck]

On Raspberry Pi Compute Module platforms, it is possible to attach a
single camera device only to the secondary Unicam port. The current
logic of PipelineHandlerRPi::match() will return a failure during
enumeration of the first Unicam media device (due to no sensor attached,
or sensor failure) and thus the second Unicam media device will never be
enumerated.

Fix this by looping over all Unicam instances in PipelineHandlerRPi::match()
until a camera is correctly registered, or return a failure otherwise.

Reported-on: https://github.com/raspberrypi/libcamera/issues/44
Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 .../pipeline/raspberrypi/raspberrypi.cpp      | 67 +++++++++++--------
 1 file changed, 40 insertions(+), 27 deletions(-)

diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
index 841209548350..ef01b7e166ba 100644
--- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
+++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
@@ -1246,41 +1246,54 @@ int PipelineHandlerRPi::queueRequestDevice(Camera *camera, Request *request)
 
 bool PipelineHandlerRPi::match(DeviceEnumerator *enumerator)
 {
-	DeviceMatch unicam("unicam");
-	MediaDevice *unicamDevice = acquireMediaDevice(enumerator, unicam);
+	constexpr unsigned int numUnicamDevices = 2;
 
-	if (!unicamDevice) {
-		LOG(RPI, Debug) << "Unable to acquire a Unicam instance";
-		return false;
-	}
+	/*
+	 * Loop over all Unicam instances, but return out once a match is found.
+	 * This is to ensure we correctly enumrate the camera when an instance
+	 * of Unicam has registered with media controller, but has not registered
+	 * device nodes due to a sensor subdevice failure.
+	 */
+	for (unsigned int i = 0; i < numUnicamDevices; i++) {
+		DeviceMatch unicam("unicam");
+		MediaDevice *unicamDevice = acquireMediaDevice(enumerator, unicam);
 
-	DeviceMatch isp("bcm2835-isp");
-	MediaDevice *ispDevice = acquireMediaDevice(enumerator, isp);
+		if (!unicamDevice) {
+			LOG(RPI, Debug) << "Unable to acquire a Unicam instance";
+			continue;
+		}
 
-	if (!ispDevice) {
-		LOG(RPI, Debug) << "Unable to acquire ISP instance";
-		return false;
-	}
+		DeviceMatch isp("bcm2835-isp");
+		MediaDevice *ispDevice = acquireMediaDevice(enumerator, isp);
 
-	/*
-	 * The loop below is used to register multiple cameras behind one or more
-	 * video mux devices that are attached to a particular Unicam instance.
-	 * Obviously these cameras cannot be used simultaneously.
-	 */
-	unsigned int numCameras = 0;
-	for (MediaEntity *entity : unicamDevice->entities()) {
-		if (entity->function() != MEDIA_ENT_F_CAM_SENSOR)
+		if (!ispDevice) {
+			LOG(RPI, Debug) << "Unable to acquire ISP instance";
 			continue;
+		}
 
-		int ret = registerCamera(unicamDevice, ispDevice, entity);
-		if (ret)
-			LOG(RPI, Error) << "Failed to register camera "
-					<< entity->name() << ": " << ret;
-		else
-			numCameras++;
+		/*
+		 * The loop below is used to register multiple cameras behind one or more
+		 * video mux devices that are attached to a particular Unicam instance.
+		 * Obviously these cameras cannot be used simultaneously.
+		 */
+		unsigned int numCameras = 0;
+		for (MediaEntity *entity : unicamDevice->entities()) {
+			if (entity->function() != MEDIA_ENT_F_CAM_SENSOR)
+				continue;
+
+			int ret = registerCamera(unicamDevice, ispDevice, entity);
+			if (ret)
+				LOG(RPI, Error) << "Failed to register camera "
+						<< entity->name() << ": " << ret;
+			else
+				numCameras++;
+		}
+
+		if (numCameras)
+			return true;
 	}
 
-	return !!numCameras;
+	return false;
 }
 
 void PipelineHandlerRPi::releaseDevice(Camera *camera)
-- 
2.25.1