libcamera: bound_method: Define connection type for method invocation

Define an enumeration of connection types to describe the delivery
method of signals and method invocation.

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

src/libcamera/bound_method.cpp

@@ -11,8 +11,42 @@
 #include "thread.h"
 #include "utils.h"
 
+/**
+ * \file bound_method.h
+ * \brief Method bind and invocation
+ */
+
 namespace libcamera {
 
+/**
+ * \enum ConnectionType
+ * \brief Connection type for asynchronous communication
+ *
+ * This enumeration describes the possible types of asynchronous communication
+ * between a sender and a receiver. It applies to Signal::emit() and
+ * Object::invokeMethod().
+ *
+ * \var ConnectionType::ConnectionTypeAuto
+ * \brief If the sender and the receiver live in the same thread,
+ * ConnectionTypeDirect is used. Otherwise ConnectionTypeQueued is used.
+ *
+ * \var ConnectionType::ConnectionTypeDirect
+ * \brief The receiver is invoked immediately and synchronously in the sender's
+ * thread.
+ *
+ * \var ConnectionType::ConnectionTypeQueued
+ * \brief The receiver is invoked asynchronously in its thread when control
+ * returns to the thread's event loop. The sender proceeds without waiting for
+ * the invocation to complete.
+ *
+ * \var ConnectionType::ConnectionTypeBlocking
+ * \brief The receiver is invoked asynchronously in its thread when control
+ * returns to the thread's event loop. The sender blocks until the receiver
+ * signals the completion of the invocation. This connection type shall not be
+ * used when the sender and receiver live in the same thread, otherwise
+ * deadlock will occur.
+ */
+
 void BoundMethodBase::activatePack(void *pack)
 {
 	if (Thread::current() == object_->thread()) {