libcamera: camera: Add helper to check for exclusive access

Some operations on the camera requires the application to have exclusive
access to the camera. To help check for this in these operations add a
helper.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/camera.h

@@ -50,6 +50,7 @@ private:
 
 	friend class PipelineHandler;
 	void disconnect();
+	int exclusiveAccess();
 
 	std::shared_ptr<PipelineHandler> pipe_;
 	std::string name_;

src/libcamera/camera.cpp

@@ -240,6 +240,23 @@ Camera::streamConfiguration(std::vector<Stream *> &streams)
  * \retval -EINVAL The configuration is not valid
  */
 int Camera::configureStreams(std::map<Stream *, StreamConfiguration> &config)
+{
+	int ret;
+
+	ret = exclusiveAccess();
+	if (ret)
+		return ret;
+
+	if (!config.size()) {
+		LOG(Camera, Error)
+			<< "Can't configure streams without a configuration";
+		return -EINVAL;
+	}
+
+	return pipe_->configureStreams(this, config);
+}
+
+int Camera::exclusiveAccess()
 {
 	if (disconnected_)
 		return -ENODEV;
@@ -247,10 +264,7 @@ int Camera::configureStreams(std::map<Stream *, StreamConfiguration> &config)
 	if (!acquired_)
 		return -EACCES;
 
-	if (!config.size())
-		return -EINVAL;
-
-	return pipe_->configureStreams(this, config);
+	return 0;
 }
 
 } /* namespace libcamera */