[libcamera-devel] [RFC 11/11] libcamera: camera: Lock the pipeline handler in acquire()

[Niklas Söderlund]

To allow more then one application using libcamera simultaneously there
can be no overlap between which cameras are in use by which user. As a
camera is part of a pipeline handler and there might be shared resources
between all cameras exposed by that pipeline handler it's not enough to
to only lock access to a single camera, all cameras from that pipeline
needs to be tied to the same process.

Allow for this by locking the whole pipeline when one of it's cameras
are acquired by the user. Other processes can still enumerate and list
all cameras in the system but cant progress a camera in a locked
pipeline handler to the Acquired state.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
 src/libcamera/camera.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index bdf14b31d8eeba9c..b3860952efa6446f 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -495,6 +495,11 @@ int Camera::acquire()
 	if (!stateIs(CameraAvailable))
 		return -EBUSY;
 
+	if (!pipe_->lock()) {
+		LOG(Camera, Info) << "Camera in use by other process";
+		return -EBUSY;
+	}
+
 	state_ = CameraAcquired;
 
 	return 0;
@@ -516,6 +521,8 @@ int Camera::release()
 	if (!stateBetween(CameraAvailable, CameraConfigured))
 		return -EBUSY;
 
+	pipe_->unlock();
+
 	state_ = CameraAvailable;
 
 	return 0;
-- 
2.21.0