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diff --git a/src/libcamera/event_notifier.cpp b/src/libcamera/event_notifier.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * event_notifier.cpp - File descriptor event notifier
+ */
+
+#include <libcamera/camera_manager.h>
+#include <libcamera/event_dispatcher.h>
+#include <libcamera/event_notifier.h>
+
+/**
+ * \file event_notifier.h
+ * \brief File descriptor event notifier
+ */
+
+namespace libcamera {
+
+/**
+ * \class EventNotifier
+ * \brief Notify of activity on a file descriptor
+ *
+ * The EventNotifier models a file descriptor event source that can be
+ * monitored. It is created with the file descriptor to be monitored and the
+ * type of event, and is enabled by default. It will emit the \ref activated
+ * signal whenever an event of the monitored type occurs on the file descriptor.
+ *
+ * Supported type of events are EventNotifier::Read, EventNotifier::Write and
+ * EventNotifier::Exception. The type is specified when constructing the
+ * notifier, and can be retrieved using the type() function. To listen to
+ * multiple event types on the same file descriptor multiple notifiers must be
+ * created.
+ *
+ * The notifier can be disabled with the setEnable() function. When the notifier
+ * is disabled it ignores events and does not emit the \ref activated signal.
+ * The notifier can then be re-enabled with the setEnable() function.
+ *
+ * Creating multiple notifiers of the same type for the same file descriptor is
+ * not allowed and results in undefined behaviour.
+ *
+ * Notifier events are detected and dispatched from the
+ * EventDispatcher::processEvents() function.
+ */
+
+/**
+ * \enum EventNotifier::Type
+ * Type of file descriptor event to listen for.
+ * \var EventNotifier::Read
+ * Data is available to be read from the file descriptor
+ * \var EventNotifier::Write
+ * Data can be written to the file descriptor
+ * \var EventNotifier::Exception
+ * An exception has occurred on the file descriptor
+ */
+
+/**
+ * \brief Construct an event notifier with a file descriptor and event type
+ * \param fd The file descriptor to monitor
+ * \param type The event type to monitor
+ */
+EventNotifier::EventNotifier(int fd, Type type)
+	: fd_(fd), type_(type), enabled_(false)
+{
+	setEnabled(true);
+}
+
+EventNotifier::~EventNotifier()
+{
+	setEnabled(false);
+}
+
+/**
+ * \fn EventNotifier::type()
+ * \brief Retrieve the type of the event being monitored
+ * \return The type of the event
+ */
+
+/**
+ * \fn EventNotifier::fd()
+ * \brief Retrieve the file descriptor being monitored
+ * \return The file descriptor
+ */
+
+/**
+ * \fn EventNotifier::enabled()
+ * \brief Retrieve the notifier state
+ * \return True if the notifier is enabled, or false otherwise
+ * \sa setEnable()
+ */
+
+/**
+ * \brief Enable or disable the notifier
+ * \param enable True to enable the notifier, false to disable it
+ *
+ * This function enables or disables the notifier. A disabled notifier ignores
+ * events and does not emit the \ref activated signal.
+ */
+void EventNotifier::setEnabled(bool enable)
+{
+	if (enabled_ == enable)
+		return;
+
+	enabled_ = enable;
+
+	EventDispatcher *dispatcher = CameraManager::instance()->eventDispatcher();
+	if (enable)
+		dispatcher->registerEventNotifier(this);
+	else
+		dispatcher->unregisterEventNotifier(this);
+}
+
+/**
+ * \var EventNotifier::activated
+ * \brief Signal emitted when the event occurs
+ *
+ * This signal is emitted when the event \ref type() occurs on the file
+ * descriptor monitored by the notifier. The notifier pointer is passed as a
+ * parameter.
+ */
+
+} /* namespace libcamera */