libcamera: device_enumerator: add DeviceInfo class

Provide a DeviceInfo class which holds all information from the initial
enumeration of a media device. Not all information available at a media
device is stored, only the information needed for a pipeline handler to
find a specific device.

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

src/libcamera/device_enumerator.cpp

@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * device_enumerator.cpp - Enumeration and matching
+ */
+
+#include "device_enumerator.h"
+#include "log.h"
+
+namespace libcamera {
+
+/* -----------------------------------------------------------------------------
+ * DeviceInfo
+ */
+
+DeviceInfo::DeviceInfo(const std::string &devnode, const struct media_device_info &info,
+		       const std::map<std::string, std::string> &entities)
+	: acquired_(false), devnode_(devnode), info_(info), entities_(entities)
+{
+	for (const auto &entity : entities_)
+		LOG(Info) << "Device: " << devnode_ << " Entity: '" << entity.first << "' -> " << entity.second;
+}
+
+int DeviceInfo::acquire()
+{
+	if (acquired_)
+		return -EBUSY;
+
+	acquired_ = true;
+
+	return 0;
+}
+
+void DeviceInfo::release()
+{
+	acquired_ = false;
+}
+
+bool DeviceInfo::busy() const
+{
+	return acquired_;
+}
+
+const std::string &DeviceInfo::devnode() const
+{
+	return devnode_;
+}
+
+const struct media_device_info &DeviceInfo::info() const
+{
+	return info_;
+}
+
+std::vector<std::string> DeviceInfo::entities() const
+{
+	std::vector<std::string> entities;
+
+	for (const auto &entity : entities_)
+		entities.push_back(entity.first);
+
+	return entities;
+}
+
+int DeviceInfo::lookup(const std::string &name, std::string &devnode) const
+{
+	auto it = entities_.find(name);
+
+	if (it == entities_.end()) {
+		LOG(Error) << "Trying to lookup entity '" << name << "' which does not exist";
+		return -ENODEV;
+	}
+
+	devnode = it->second;
+	return 0;
+}
+
+} /* namespace libcamera */

src/libcamera/include/device_enumerator.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * device_enumerator.h - API to enumerate and find media devices
+ */
+#ifndef __LIBCAMERA_DEVICE_ENUMERATOR_H__
+#define __LIBCAMERA_DEVICE_ENUMERATOR_H__
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include <linux/media.h>
+
+namespace libcamera {
+
+class DeviceInfo
+{
+public:
+	DeviceInfo(const std::string &devnode, const struct media_device_info &info,
+		   const std::map<std::string, std::string> &entities);
+
+	int acquire();
+	void release();
+	bool busy() const;
+
+	const std::string &devnode() const;
+	const struct media_device_info &info() const;
+	std::vector<std::string> entities() const;
+
+	int lookup(const std::string &name, std::string &devnode) const;
+
+private:
+	bool acquired_;
+
+	std::string devnode_;
+	struct media_device_info info_;
+	std::map<std::string, std::string> entities_;
+};
+
+} /* namespace libcamera */
+
+#endif	/* __LIBCAMERA_DEVICE_ENUMERATOR_H__ */

src/libcamera/meson.build

@@ -1,10 +1,12 @@
 libcamera_sources = files([
     'camera.cpp',
+    'device_enumerator.cpp',
     'log.cpp',
     'main.cpp',
 ])
 
 libcamera_headers = files([
+    'include/device_enumerator.h',
     'include/log.h',
     'include/utils.h',
 ])