libcamera: camera: Add disconnection notification

As camera object have the potential to outlive the hardware they
represent, there is a need to inform the camera that the underlying
device has been disconnected, and in turn to notify applications.

Implement a disconnection notification mechanism that can be used by
pipeline handlers to notify the camera of disconnection. The camera then
block all new API calls and emit the disconnected signal.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index efafb9e2..a2ded62d 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -10,6 +10,8 @@
 #include <memory>
 #include <string>
 
+#include <libcamera/signal.h>
+
 namespace libcamera {
 
 class PipelineHandler;
@@ -25,10 +27,15 @@ public:
 
 	const std::string &name() const;
 
+	Signal<Camera *> disconnected;
+
 private:
 	Camera(PipelineHandler *pipe, const std::string &name);
 	~Camera();
 
+	friend class PipelineHandler;
+	void disconnect();
+
 	std::shared_ptr<PipelineHandler> pipe_;
 	std::string name_;
 };
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 3a531c7e..9cec2892 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -34,6 +34,8 @@
 
 namespace libcamera {
 
+LOG_DECLARE_CATEGORY(Camera)
+
 /**
  * \class Camera
  * \brief Camera device
@@ -87,6 +89,18 @@ const std::string &Camera::name() const
 	return name_;
 }
 
+/**
+ * \var Camera::disconnected
+ * \brief Signal emitted when the camera is disconnected from the system
+ *
+ * This signal is emitted when libcamera detects that the cameera has been
+ * removed from the system. For hot-pluggable devices this is usually caused by
+ * physical device disconnection. The media device is passed as a parameter.
+ *
+ * As soon as this signal is emitted the camera instance will refuse all new
+ * application API calls by returning errors immediately.
+ */
+
 Camera::Camera(PipelineHandler *pipe, const std::string &name)
 	: pipe_(pipe->shared_from_this()), name_(name)
 {
@@ -96,4 +110,21 @@ Camera::~Camera()
 {
 }
 
+/**
+ * \brief Notify camera disconnection
+ *
+ * This method is used to notify the camera instance that the underlying
+ * hardware has been unplugged. In response to the disconnection the camera
+ * instance notifies the application by emitting the #disconnected signal, and
+ * ensures that all new calls to the application-facing Camera API return an
+ * error immediately.
+ */
+void Camera::disconnect()
+{
+	LOG(Camera, Debug) << "Disconnecting camera " << name_;
+
+	/** \todo Block API calls when they will be implemented. */
+	disconnected.emit(this);
+}
+
 } /* namespace libcamera */