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>

src/v4l2/v4l2_camera.cpp

@@ -0,0 +1,224 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_camera.cpp - V4L2 compatibility camera
+ */
+
+#include "v4l2_camera.h"
+
+#include <errno.h>
+
+#include "log.h"
+#include "utils.h"
+
+using namespace libcamera;
+
+LOG_DECLARE_CATEGORY(V4L2Compat);
+
+FrameMetadata::FrameMetadata(Buffer *buffer)
+	: index_(buffer->index()), bytesused_(buffer->bytesused()),
+	  timestamp_(buffer->timestamp()), sequence_(buffer->sequence()),
+	  status_(buffer->status())
+{
+}
+
+V4L2Camera::V4L2Camera(std::shared_ptr<Camera> camera)
+	: camera_(camera), isRunning_(false)
+{
+	camera_->requestCompleted.connect(this, &V4L2Camera::requestComplete);
+}
+
+V4L2Camera::~V4L2Camera()
+{
+	camera_->release();
+}
+
+void V4L2Camera::open(int *ret)
+{
+	/* \todo Support multiple open. */
+	if (camera_->acquire() < 0) {
+		LOG(V4L2Compat, Error) << "Failed to acquire camera";
+		*ret = -EINVAL;
+		return;
+	}
+
+	config_ = camera_->generateConfiguration({ StreamRole::Viewfinder });
+	if (!config_) {
+		camera_->release();
+		*ret = -EINVAL;
+		return;
+	}
+
+	*ret = 0;
+}
+
+void V4L2Camera::close()
+{
+	camera_->release();
+}
+
+void V4L2Camera::getStreamConfig(StreamConfiguration *streamConfig)
+{
+	*streamConfig = config_->at(0);
+}
+
+std::vector<FrameMetadata> V4L2Camera::completedBuffers()
+{
+	std::vector<FrameMetadata> v;
+
+	bufferLock_.lock();
+	for (std::unique_ptr<FrameMetadata> &metadata : completedBuffers_)
+		v.push_back(*metadata.get());
+	completedBuffers_.clear();
+	bufferLock_.unlock();
+
+	return v;
+}
+
+void V4L2Camera::requestComplete(Request *request)
+{
+	if (request->status() == Request::RequestCancelled)
+		return;
+
+	/* We only have one stream at the moment. */
+	bufferLock_.lock();
+	Buffer *buffer = request->buffers().begin()->second;
+	std::unique_ptr<FrameMetadata> metadata =
+		utils::make_unique<FrameMetadata>(buffer);
+	completedBuffers_.push_back(std::move(metadata));
+	bufferLock_.unlock();
+
+	bufferSema_.release();
+}
+
+void V4L2Camera::configure(int *ret, StreamConfiguration *streamConfigOut,
+			   const Size &size, PixelFormat pixelformat,
+			   unsigned int bufferCount)
+{
+	StreamConfiguration &streamConfig = config_->at(0);
+	streamConfig.size.width = size.width;
+	streamConfig.size.height = size.height;
+	streamConfig.pixelFormat = pixelformat;
+	streamConfig.bufferCount = bufferCount;
+	/* \todo memoryType (interval vs external) */
+
+	CameraConfiguration::Status validation = config_->validate();
+	if (validation == CameraConfiguration::Invalid) {
+		LOG(V4L2Compat, Debug) << "Configuration invalid";
+		*ret = -EINVAL;
+		return;
+	}
+	if (validation == CameraConfiguration::Adjusted)
+		LOG(V4L2Compat, Debug) << "Configuration adjusted";
+
+	LOG(V4L2Compat, Debug) << "Validated configuration is: "
+			      << streamConfig.toString();
+
+	*ret = camera_->configure(config_.get());
+	if (*ret < 0)
+		return;
+
+	*streamConfigOut = config_->at(0);
+}
+
+void V4L2Camera::mmap(void **ret, unsigned int index)
+{
+	Stream *stream = *camera_->streams().begin();
+	*ret = stream->buffers()[index].planes()[0].mem();
+}
+
+void V4L2Camera::allocBuffers(int *ret, unsigned int count)
+{
+	*ret = camera_->allocateBuffers();
+	if (*ret == -EACCES)
+		*ret = -EBUSY;
+}
+
+void V4L2Camera::freeBuffers()
+{
+	camera_->freeBuffers();
+}
+
+void V4L2Camera::streamOn(int *ret)
+{
+	*ret = 0;
+
+	if (isRunning_)
+		return;
+
+	*ret = camera_->start();
+	if (*ret < 0) {
+		if (*ret == -EACCES)
+			*ret = -EBUSY;
+		return;
+	}
+	isRunning_ = true;
+
+	for (std::unique_ptr<Request> &req : pendingRequests_) {
+		/* \todo What should we do if this returns -EINVAL? */
+		*ret = camera_->queueRequest(req.release());
+		if (*ret < 0) {
+			if (*ret == -EACCES)
+				*ret = -EBUSY;
+			return;
+		}
+	}
+
+	pendingRequests_.clear();
+}
+
+void V4L2Camera::streamOff(int *ret)
+{
+	*ret = 0;
+
+	/* \todo Restore buffers to reqbufs state? */
+	if (!isRunning_)
+		return;
+
+	*ret = camera_->stop();
+	if (*ret < 0) {
+		if (*ret == -EACCES)
+			*ret = -EBUSY;
+		return;
+	}
+	isRunning_ = false;
+}
+
+void V4L2Camera::qbuf(int *ret, unsigned int index)
+{
+	Stream *stream = config_->at(0).stream();
+	std::unique_ptr<Buffer> buffer = stream->createBuffer(index);
+	if (!buffer) {
+		LOG(V4L2Compat, Error) << "Can't create buffer";
+		*ret = -ENOMEM;
+		return;
+	}
+
+	std::unique_ptr<Request> request =
+		std::unique_ptr<Request>(camera_->createRequest());
+	if (!request) {
+		LOG(V4L2Compat, Error) << "Can't create request";
+		*ret = -ENOMEM;
+		return;
+	}
+
+	*ret = request->addBuffer(std::move(buffer));
+	if (*ret < 0) {
+		LOG(V4L2Compat, Error) << "Can't set buffer for request";
+		*ret = -ENOMEM;
+		return;
+	}
+
+	if (!isRunning_) {
+		pendingRequests_.push_back(std::move(request));
+		return;
+	}
+
+	*ret = camera_->queueRequest(request.release());
+	if (*ret < 0) {
+		LOG(V4L2Compat, Error) << "Can't queue request";
+		if (*ret == -EACCES)
+			*ret = -EBUSY;
+	}
+}