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, 81 insertions, 0 deletions

diff --git a/src/v4l2/v4l2_camera_proxy.h b/src/v4l2/v4l2_camera_proxy.h
new file mode 100644
index 00000000..bef0f0af
--- /dev/null
+++ b/src/v4l2/v4l2_camera_proxy.h
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_camera_proxy.h - Proxy to V4L2 compatibility camera
+ */
+
+#ifndef __V4L2_CAMERA_PROXY_H__
+#define __V4L2_CAMERA_PROXY_H__
+
+#include <linux/videodev2.h>
+#include <map>
+#include <memory>
+#include <sys/types.h>
+#include <vector>
+
+#include <libcamera/camera.h>
+
+#include "v4l2_camera.h"
+
+using namespace libcamera;
+
+class V4L2CameraProxy
+{
+public:
+	V4L2CameraProxy(unsigned int index, std::shared_ptr<Camera> camera);
+
+	int open(bool nonBlocking);
+	void dup();
+	void close();
+	void *mmap(size_t length, int prot, int flags, off_t offset);
+	int munmap(void *addr, size_t length);
+
+	int ioctl(unsigned long request, void *arg);
+
+private:
+	bool validateBufferType(uint32_t type);
+	bool validateMemoryType(uint32_t memory);
+	void setFmtFromConfig(StreamConfiguration &streamConfig);
+	unsigned int calculateSizeImage(StreamConfiguration &streamConfig);
+	void querycap(std::shared_ptr<Camera> camera);
+	void updateBuffers();
+	int freeBuffers();
+
+	int vidioc_querycap(struct v4l2_capability *arg);
+	int vidioc_enum_fmt(struct v4l2_fmtdesc *arg);
+	int vidioc_g_fmt(struct v4l2_format *arg);
+	int vidioc_s_fmt(struct v4l2_format *arg);
+	int vidioc_try_fmt(struct v4l2_format *arg);
+	int vidioc_reqbufs(struct v4l2_requestbuffers *arg);
+	int vidioc_querybuf(struct v4l2_buffer *arg);
+	int vidioc_qbuf(struct v4l2_buffer *arg);
+	int vidioc_dqbuf(struct v4l2_buffer *arg);
+	int vidioc_streamon(int *arg);
+	int vidioc_streamoff(int *arg);
+
+	static int bplMultiplier(unsigned int format);
+	static int imageSize(unsigned int format, unsigned int width,
+			     unsigned int height);
+
+	static unsigned int v4l2ToDrm(unsigned int pixelformat);
+	static unsigned int drmToV4L2(unsigned int pixelformat);
+
+	unsigned int refcount_;
+	unsigned int index_;
+	bool nonBlocking_;
+
+	struct v4l2_format curV4L2Format_;
+	StreamConfiguration streamConfig_;
+	struct v4l2_capability capabilities_;
+	unsigned int bufferCount_;
+	unsigned int currentBuf_;
+	unsigned int sizeimage_;
+
+	std::vector<struct v4l2_buffer> buffers_;
+	std::map<void *, unsigned int> mmaps_;
+
+	std::unique_ptr<V4L2Camera> vcam_;
+};
+
+#endif /* __V4L2_CAMERA_PROXY_H__ */