libcamera: Provide a Request object

Implement a Request object used by applications to queue image capture
requests to a camera.

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>
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

include/libcamera/camera.h

@@ -11,10 +11,12 @@
 #include <memory>
 #include <string>
 
+#include <libcamera/request.h>
 #include <libcamera/signal.h>
 
 namespace libcamera {
 
+class Buffer;
 class PipelineHandler;
 class Stream;
 class StreamConfiguration;
@@ -31,6 +33,7 @@ public:
 
 	const std::string &name() const;
 
+	Signal<Request *, const std::map<Stream *, Buffer *> &> requestCompleted;
 	Signal<Camera *> disconnected;
 
 	int acquire();

include/libcamera/libcamera.h

@@ -12,6 +12,7 @@
 #include <libcamera/camera_manager.h>
 #include <libcamera/event_dispatcher.h>
 #include <libcamera/event_notifier.h>
+#include <libcamera/request.h>
 #include <libcamera/signal.h>
 #include <libcamera/stream.h>
 #include <libcamera/timer.h>

include/libcamera/meson.build

@@ -5,6 +5,7 @@ libcamera_api = files([
     'event_dispatcher.h',
     'event_notifier.h',
     'libcamera.h',
+    'request.h',
     'signal.h',
     'stream.h',
     'timer.h',

include/libcamera/request.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * request.h - Capture request handling
+ */
+#ifndef __LIBCAMERA_REQUEST_H__
+#define __LIBCAMERA_REQUEST_H__
+
+#include <map>
+#include <unordered_set>
+
+#include <libcamera/signal.h>
+
+namespace libcamera {
+
+class Buffer;
+class Camera;
+class Stream;
+
+class Request
+{
+public:
+	explicit Request(Camera *camera);
+	Request(const Request &) = delete;
+	Request &operator=(const Request &) = delete;
+
+	int setBuffers(const std::map<Stream *, Buffer *> &streamMap);
+	Buffer *findBuffer(Stream *stream) const;
+
+private:
+	friend class Camera;
+
+	int prepare();
+	void bufferCompleted(Buffer *buffer);
+
+	Camera *camera_;
+	std::map<Stream *, Buffer *> bufferMap_;
+	std::unordered_set<Buffer *> pending_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_REQUEST_H__ */

src/libcamera/camera.cpp

@@ -97,6 +97,11 @@ const std::string &Camera::name() const
 	return name_;
 }
 
+/**
+ * \var Camera::requestCompleted
+ * \brief Signal emitted when a request queued to the camera has completed
+ */
+
 /**
  * \var Camera::disconnected
  * \brief Signal emitted when the camera is disconnected from the system

src/libcamera/meson.build

@@ -11,6 +11,7 @@ libcamera_sources = files([
     'media_device.cpp',
     'media_object.cpp',
     'pipeline_handler.cpp',
+    'request.cpp',
     'signal.cpp',
     'stream.cpp',
     'timer.cpp',

src/libcamera/request.cpp

@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * request.cpp - Capture request handling
+ */
+
+#include <map>
+
+#include <libcamera/buffer.h>
+#include <libcamera/camera.h>
+#include <libcamera/request.h>
+#include <libcamera/stream.h>
+
+#include "log.h"
+
+/**
+ * \file request.h
+ * \brief Describes a frame capture request to be processed by a camera
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(Request)
+
+/**
+ * \class Request
+ * \brief A frame capture request
+ *
+ * A Request allows an application to associate buffers and controls on a
+ * per-frame basis to be queued to the camera device for processing.
+ */
+
+/**
+ * \brief Create a capture request for a camera
+ * \param[in] camera The camera that creates the request
+ */
+Request::Request(Camera *camera)
+	: camera_(camera)
+{
+}
+
+/**
+ * \brief Set the streams to capture with associated buffers
+ * \param[in] streamMap The map of streams to buffers
+ * \return 0 on success or a negative error code otherwise
+ * \retval -EBUSY Buffers have already been set
+ */
+int Request::setBuffers(const std::map<Stream *, Buffer *> &streamMap)
+{
+	if (!bufferMap_.empty()) {
+		LOG(Request, Error) << "Buffers already set";
+		return -EBUSY;
+	}
+
+	bufferMap_ = streamMap;
+	return 0;
+}
+
+/**
+ * \var Request::bufferMap_
+ * \brief Mapping of streams to buffers for this request
+ *
+ * The bufferMap_ tracks the buffers associated with each stream. If a stream is
+ * not utilised in this request there will be no buffer for that stream in the
+ * map.
+ */
+
+/**
+ * \brief Return the buffer associated with a stream
+ * \param[in] stream The stream the buffer is associated to
+ *
+ * \return The buffer associated with the stream, or nullptr if the stream is
+ * not part of this request
+ */
+Buffer *Request::findBuffer(Stream *stream) const
+{
+	auto it = bufferMap_.find(stream);
+	if (it == bufferMap_.end())
+		return nullptr;
+
+	return it->second;
+}
+
+/**
+ * \brief Prepare the resources for the completion handler
+ */
+int Request::prepare()
+{
+	for (auto const &pair : bufferMap_) {
+		Buffer *buffer = pair.second;
+		buffer->completed.connect(this, &Request::bufferCompleted);
+		pending_.insert(buffer);
+	}
+
+	return 0;
+}
+
+/**
+ * \brief Slot for the buffer completed signal
+ *
+ * The bufferCompleted method serves as slot where to connect the
+ * Buffer::completed signal that is emitted when a buffer has available
+ * data.
+ *
+ * The request completes when all the buffers it contains are ready to be
+ * presented to the application.
+ */
+void Request::bufferCompleted(Buffer *buffer)
+{
+	buffer->completed.disconnect(this, &Request::bufferCompleted);
+
+	int ret = pending_.erase(buffer);
+	ASSERT(ret == 1);
+
+	if (pending_.empty()) {
+		std::map<Stream *, Buffer *> buffers(std::move(bufferMap_));
+		camera_->requestCompleted.emit(this, buffers);
+	}
+}
+
+} /* namespace libcamera */