v4l2: v4l2_compat: Add V4L2 compatibility layer

Add libcamera V4L2 compatibility layer.

This initial implementation supports the minimal set of V4L2 operations,
which allows getting, setting, and enumerating formats, and streaming
frames from a video device. Some data about the wrapped V4L2 video
device are hardcoded.

Add a build option named 'v4l2' and adjust the build system to
selectively compile the V4L2 compatibility layer.

For now we match the V4L2 device node to a libcamera camera based on a
devnum that a pipeline handler may optionally map to a libcamera
camera.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/src/v4l2/v4l2_compat_manager.h b/src/v4l2/v4l2_compat_manager.h
new file mode 100644
index 00000000..dd9d3210
--- /dev/null
+++ b/src/v4l2/v4l2_compat_manager.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_compat_manager.h - V4L2 compatibility manager
+ */
+
+#ifndef __V4L2_COMPAT_MANAGER_H__
+#define __V4L2_COMPAT_MANAGER_H__
+
+#include <condition_variable>
+#include <fcntl.h>
+#include <map>
+#include <memory>
+#include <mutex>
+#include <sys/types.h>
+#include <vector>
+
+#include <libcamera/camera_manager.h>
+
+#include "thread.h"
+#include "v4l2_camera_proxy.h"
+
+using namespace libcamera;
+
+class V4L2CompatManager : public Thread
+{
+public:
+	static V4L2CompatManager *instance();
+
+	int init();
+
+	V4L2CameraProxy *getProxy(int fd);
+
+	int openat(int dirfd, const char *path, int oflag, mode_t mode);
+
+	int dup(int oldfd);
+	int close(int fd);
+	void *mmap(void *addr, size_t length, int prot, int flags,
+		   int fd, off_t offset);
+	int munmap(void *addr, size_t length);
+	int ioctl(int fd, unsigned long request, void *arg);
+
+private:
+	V4L2CompatManager();
+	~V4L2CompatManager();
+
+	void run() override;
+	int getCameraIndex(int fd);
+
+	typedef int (*openat_func_t)(int dirfd, const char *path, int oflag, ...);
+	typedef int (*dup_func_t)(int oldfd);
+	typedef int (*close_func_t)(int fd);
+	typedef int (*ioctl_func_t)(int fd, unsigned long request, ...);
+	typedef void *(*mmap_func_t)(void *addr, size_t length, int prot,
+				     int flags, int fd, off_t offset);
+	typedef int (*munmap_func_t)(void *addr, size_t length);
+
+	openat_func_t openat_func_;
+	dup_func_t    dup_func_;
+	close_func_t  close_func_;
+	ioctl_func_t  ioctl_func_;
+	mmap_func_t   mmap_func_;
+	munmap_func_t munmap_func_;
+
+	CameraManager *cm_;
+
+	std::mutex mutex_;
+	std::condition_variable cv_;
+	bool initialized_;
+
+	std::vector<std::unique_ptr<V4L2CameraProxy>> proxies_;
+	std::map<int, V4L2CameraProxy *> devices_;
+	std::map<void *, V4L2CameraProxy *> mmaps_;
+};
+
+#endif /* __V4L2_COMPAT_MANAGER_H__ */