[libcamera-devel] [PATCH v3 2/3] libcamera: Add V4L2 Device object

[Kieran Bingham]

Provide a helper V4L2 device object capable of interacting with the
V4L2 Linux Kernel APIs.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/libcamera/include/v4l2_device.h |  45 +++++++++
 src/libcamera/meson.build           |   2 +
 src/libcamera/v4l2_device.cpp       | 150 ++++++++++++++++++++++++++++
 3 files changed, 197 insertions(+)
 create mode 100644 src/libcamera/include/v4l2_device.h
 create mode 100644 src/libcamera/v4l2_device.cpp

diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
new file mode 100644
index 000000000000..b0f5e9689654
--- /dev/null
+++ b/src/libcamera/include/v4l2_device.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_device.h - V4L2 Device
+ */
+#ifndef __LIBCAMERA_V4L2_DEVICE_H__
+#define __LIBCAMERA_V4L2_DEVICE_H__
+
+#include <string>
+
+#include <linux/videodev2.h>
+
+namespace libcamera {
+
+class V4L2Capability : public v4l2_capability
+{
+public:
+	std::string getDriver() const { return std::string((char *)driver); }
+	std::string getCard() const { return std::string((char *)card); }
+
+	bool isCapture() const { return capabilities & V4L2_CAP_VIDEO_CAPTURE; }
+	bool hasStreaming() const { return capabilities & V4L2_CAP_STREAMING; }
+};
+
+class V4L2Device
+{
+public:
+	V4L2Device() = delete;
+	V4L2Device(const std::string &devnode);
+	~V4L2Device();
+
+	int open();
+	bool isOpen() const;
+	void close();
+
+private:
+	std::string devnode_;
+	int fd_;
+	V4L2Capability caps_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_V4L2_DEVICE_H__ */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index abf9a71d4172..f9f25c0ecf15 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -11,6 +11,7 @@ libcamera_sources = files([
     'pipeline_handler.cpp',
     'signal.cpp',
     'timer.cpp',
+    'v4l2_device.cpp',
 ])
 
 libcamera_headers = files([
@@ -21,6 +22,7 @@ libcamera_headers = files([
     'include/media_object.h',
     'include/pipeline_handler.h',
     'include/utils.h',
+    'include/v4l2_device.h',
 ])
 
 libcamera_internal_includes =  include_directories('include')
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
new file mode 100644
index 000000000000..8c49d3ff56e2
--- /dev/null
+++ b/src/libcamera/v4l2_device.cpp
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_device.cpp - V4L2 Device
+ */
+
+#include <fcntl.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "log.h"
+#include "v4l2_device.h"
+
+/**
+ * \file v4l2_device.h
+ * \brief V4L2 Device API
+ */
+namespace libcamera {
+
+/**
+ * \class V4L2Capability
+ * \brief struct v4l2_capability object wrapper and helpers
+ *
+ * The V4L2Capability class manages the information returned by the
+ * VIDIOC_QUERYCAP ioctl.
+ */
+
+/**
+ * \fn std::string V4L2Capability::getDriver()
+ * \brief Retrieve the driver module name
+ * \return The string containing the name of the driver module
+ */
+
+/**
+ * \fn std::string V4L2Capability::getCard()
+ * \brief Retrieve the device card name
+ * \return The string containing the device name
+ */
+
+/**
+ * \fn bool V4L2Capability::isCapture()
+ * \brief Identify if the device is capable of capturing video
+ * \return boolean true if the device provides video frames
+ */
+
+/**
+ * \fn bool V4L2Capability::hasStreaming()
+ * \brief Determine if the device can perform Streaming IO
+ * \return boolean true if the device provides Streaming IO IOCTLs
+ */
+
+/**
+ * \class V4L2Device
+ * \brief V4L2Device object and API.
+ *
+ * The V4L2 Device API class models an instance of a V4L2 device node.
+ * It is constructed with the path to a V4L2 video device node. The device node
+ * is only opened upon a call to open() which must be checked for success.
+ *
+ * The device capabilities are validated and the device is rejected if it is
+ * not a suitable capture device.
+ *
+ * No API call (except open(), isOpen() and close()) shall be called on an
+ * unopened device instance.
+ *
+ * Upon destruction any device left open will be closed, and any resources
+ * released.
+ */
+
+/**
+ * \brief Construct a V4L2Device
+ * \param devnode The file-system path to the video device node
+ */
+V4L2Device::V4L2Device(const std::string &devnode)
+	: devnode_(devnode), fd_(-1)
+{
+}
+
+V4L2Device::~V4L2Device()
+{
+	close();
+}
+
+/**
+ * \brief Open a V4L2 device and query properties from the device.
+ * \return 0 on success, or a negative error code otherwise
+ */
+int V4L2Device::open()
+{
+	int ret;
+
+	if (isOpen()) {
+		LOG(Error) << "Device already open";
+		return -EBUSY;
+	}
+
+	ret = ::open(devnode_.c_str(), O_RDWR);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(Error) << "Failed to open V4L2 device " << devnode_
+			   << " : " << strerror(ret);
+		return ret;
+	}
+	fd_ = ret;
+
+	ret = ioctl(fd_, VIDIOC_QUERYCAP, &caps_);
+	if (ret < 0) {
+		LOG(Error) << "Failed to query device capabilities: " << strerror(errno);
+		return -errno;
+	}
+
+	LOG(Debug) << "Opened '" << devnode_ << "' " << caps_.getDriver() << ": " << caps_.getCard();
+
+	if (!(caps_.isCapture())) {
+		LOG(Error) << "Device is not a capture device";
+		return -EINVAL;
+	}
+
+	if (!(caps_.hasStreaming())) {
+		LOG(Error) << "Device does not support streaming IO";
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * \brief Check if device is successfully opened
+ */
+bool V4L2Device::isOpen() const
+{
+	return (fd_ != -1);
+}
+
+/**
+ * \brief Close the device, releasing any resources acquired by open()
+ */
+void V4L2Device::close()
+{
+	if (fd_ < 0)
+		return;
+
+	::close(fd_);
+	fd_ = -1;
+}
+
+} /* namespace libcamera */
-- 
2.17.1