[libcamera-devel] [PATCH] libcamera: CameraManager, PipelineHandler: Allow multiple devnums per camera

[Paul Elder]

The V4L2 compatibility layer uses devnum to match video device nodes to
libcamera Cameras. Some pipeline handlers don't report a devnum for
their camera, which prevents the V4L2 compatibility layer from matching
video device nodes to these cameras. To fix this, we first allow the
camera manager to map multiple devnums to a camera. Next, if the pipeline
handler doesn't report a devnum for a camera, then walk the media device
and entity list and tell the camera manager to map every one of these
devnums to the camera.

We considered walking the media entity list and taking the devnum from
just the one with the default flag set, but we found that some drivers
(eg. vimc) don't set this flag for any entity.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
---
 include/libcamera/camera_manager.h |  3 ++-
 src/libcamera/camera_manager.cpp   | 14 ++++++++------
 src/libcamera/pipeline_handler.cpp | 12 +++++++++++-
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/include/libcamera/camera_manager.h b/include/libcamera/camera_manager.h
index 079f848a..6095b799 100644
--- a/include/libcamera/camera_manager.h
+++ b/include/libcamera/camera_manager.h
@@ -34,7 +34,8 @@ public:
 	std::shared_ptr<Camera> get(const std::string &name);
 	std::shared_ptr<Camera> get(dev_t devnum);
 
-	void addCamera(std::shared_ptr<Camera> camera, dev_t devnum);
+	void addCamera(std::shared_ptr<Camera> camera,
+		       std::vector<dev_t> devnums);
 	void removeCamera(Camera *camera);
 
 	static const std::string &version() { return version_; }
diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
index da806fa7..fa0bd6a0 100644
--- a/src/libcamera/camera_manager.cpp
+++ b/src/libcamera/camera_manager.cpp
@@ -36,7 +36,8 @@ public:
 	Private(CameraManager *cm);
 
 	int start();
-	void addCamera(std::shared_ptr<Camera> &camera, dev_t devnum);
+	void addCamera(std::shared_ptr<Camera> &camera,
+		       std::vector<dev_t> devnums);
 	void removeCamera(Camera *camera);
 
 	/*
@@ -168,7 +169,7 @@ void CameraManager::Private::cleanup()
 }
 
 void CameraManager::Private::addCamera(std::shared_ptr<Camera> &camera,
-				       dev_t devnum)
+				       std::vector<dev_t> devnums)
 {
 	MutexLocker locker(mutex_);
 
@@ -183,7 +184,7 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> &camera,
 
 	cameras_.push_back(std::move(camera));
 
-	if (devnum) {
+	for (dev_t devnum : devnums) {
 		unsigned int index = cameras_.size() - 1;
 		camerasByDevnum_[devnum] = cameras_[index];
 	}
@@ -374,7 +375,7 @@ std::shared_ptr<Camera> CameraManager::get(dev_t devnum)
 /**
  * \brief Add a camera to the camera manager
  * \param[in] camera The camera to be added
- * \param[in] devnum The device number to associate with \a camera
+ * \param[in] devnums The device numbers to associate with \a camera
  *
  * This function is called by pipeline handlers to register the cameras they
  * handle with the camera manager. Registered cameras are immediately made
@@ -385,11 +386,12 @@ std::shared_ptr<Camera> CameraManager::get(dev_t devnum)
  *
  * \context This function shall be called from the CameraManager thread.
  */
-void CameraManager::addCamera(std::shared_ptr<Camera> camera, dev_t devnum)
+void CameraManager::addCamera(std::shared_ptr<Camera> camera,
+			      std::vector<dev_t> devnums)
 {
 	ASSERT(Thread::current() == p_.get());
 
-	p_->addCamera(camera, devnum);
+	p_->addCamera(camera, devnums);
 }
 
 /**
diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
index 53aeebdc..b3824a5f 100644
--- a/src/libcamera/pipeline_handler.cpp
+++ b/src/libcamera/pipeline_handler.cpp
@@ -502,7 +502,17 @@ void PipelineHandler::registerCamera(std::shared_ptr<Camera> camera,
 	data->camera_ = camera.get();
 	cameraData_[camera.get()] = std::move(data);
 	cameras_.push_back(camera);
-	manager_->addCamera(std::move(camera), devnum);
+
+	std::vector<dev_t> devnums;
+	if (devnum != 0)
+		devnums.push_back(devnum);
+	else
+		for (const std::shared_ptr<MediaDevice> media : mediaDevices_)
+			for (const MediaEntity *entity : media->entities())
+				devnums.push_back(makedev(entity->deviceMajor(),
+							  entity->deviceMinor()));
+
+	manager_->addCamera(std::move(camera), devnums);
 }
 
 /**
-- 
2.20.1