libcamera: Add V4L2Subdevice

Add V4L2Subdevice class that provides an interface to interact with
V4L2 defined sub-devices.

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

src/libcamera/include/v4l2_subdevice.h

@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_subdevice.h - V4L2 Subdevice
+ */
+#ifndef __LIBCAMERA_V4L2_SUBDEVICE_H__
+#define __LIBCAMERA_V4L2_SUBDEVICE_H__
+
+#include <string>
+
+namespace libcamera {
+
+struct Rectangle;
+
+struct V4L2SubdeviceFormat {
+	uint32_t mbus_code;
+	uint32_t width;
+	uint32_t height;
+};
+
+class V4L2Subdevice
+{
+public:
+	explicit V4L2Subdevice(const MediaEntity *entity);
+	V4L2Subdevice(const V4L2Subdevice &) = delete;
+	V4L2Subdevice &operator=(const V4L2Subdevice &) = delete;
+
+	int open();
+	bool isOpen() const;
+	void close();
+
+	std::string deviceNode() const { return deviceNode_; }
+
+	int setCrop(unsigned int pad, Rectangle *rect);
+	int setCompose(unsigned int pad, Rectangle *rect);
+
+	int getFormat(unsigned int pad, V4L2SubdeviceFormat *format);
+	int setFormat(unsigned int pad, V4L2SubdeviceFormat *format);
+
+private:
+	int setSelection(unsigned int pad, unsigned int target,
+			 Rectangle *rect);
+
+	std::string deviceNode_;
+	int fd_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_V4L2_SUBDEVICE_H__ */

src/libcamera/meson.build

@@ -15,6 +15,7 @@ libcamera_sources = files([
     'stream.cpp',
     'timer.cpp',
     'v4l2_device.cpp',
+    'v4l2_subdevice.cpp',
 ])
 
 libcamera_headers = files([

src/libcamera/v4l2_subdevice.cpp

@@ -0,0 +1,265 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_subdevice.cpp - V4L2 Subdevice
+ */
+
+#include <fcntl.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#include <linux/v4l2-subdev.h>
+
+#include "geometry.h"
+#include "log.h"
+#include "media_object.h"
+#include "v4l2_subdevice.h"
+
+/**
+ * \file v4l2_subdevice.h
+ * \brief V4L2 Subdevice API
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(V4L2Subdev)
+
+/**
+ * \struct V4L2SubdeviceFormat
+ * \brief The V4L2 sub-device image format and sizes
+ *
+ * This structure describes the format of images when transported between
+ * separate components connected through a physical bus, such as image sensor
+ * and image receiver or between components part of the same System-on-Chip that
+ * realize an image transformation pipeline.
+ *
+ * The format of images when transported on physical interconnections is known
+ * as the "media bus format", and it is identified by a resolution and a pixel
+ * format identification code, known as the "media bus code", not to be confused
+ * with the fourcc code that identify the format of images when stored in memory
+ * (see V4L2Device::V4L2DeviceFormat).
+ *
+ * Media Bus formats supported by the V4L2 APIs are described in Section
+ * 4.15.3.4.1 of the "Part I - Video for Linux API" chapter of the "Linux Media
+ * Infrastructure userspace API", part of the Linux kernel documentation.
+ *
+ * Image media bus formats are properties of the subdev pads.  When images are
+ * transported between two media pads identified by a 0-indexed number, the
+ * image bus format configured on the two pads should match (according to the
+ * underlying driver format matching criteria) in order to prepare for a
+ * successful streaming operation. For a more detailed description of the image
+ * format negotiation process when performed between V4L2 subdevices, refer to
+ * Section 4.15.3.1 of the above mentioned Linux kernel documentation section.
+ */
+
+/**
+ * \var V4L2SubdeviceFormat::width
+ * \brief The image width in pixels
+ */
+
+/**
+ * \var V4L2SubdeviceFormat::height
+ * \brief The image height in pixels
+ */
+
+/**
+ * \var V4L2SubdeviceFormat::mbus_code
+ * \brief The image format bus code
+ */
+
+/**
+ * \class V4L2Subdevice
+ * \brief A V4L2 subdevice as exposed by the Linux kernel
+ *
+ * The V4L2Subdevice class provides an API to the "Sub-device interface" as
+ * described in section 4.15 of the "Linux Media Infrastructure userspace API"
+ * chapter of the Linux Kernel documentation.
+ *
+ * A V4L2Subdevice is constructed from a MediaEntity instance, using the system
+ * path of the entity's device node. No API call other than 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 Create a V4L2 subdevice from a MediaEntity using its device node
+ * path
+ */
+V4L2Subdevice::V4L2Subdevice(const MediaEntity *entity)
+	: deviceNode_(entity->deviceNode()), fd_(-1)
+{
+}
+
+/**
+ * \brief Open a V4L2 subdevice
+ *
+ * \return 0 on success, a negative error code otherwise
+ */
+int V4L2Subdevice::open()
+{
+	int ret;
+
+	if (isOpen()) {
+		LOG(V4L2Subdev, Error) << "Device already open";
+		return -EBUSY;
+	}
+
+	ret = ::open(deviceNode_.c_str(), O_RDWR);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2Subdev, Error)
+			<< "Failed to open V4L2 subdevice '" << deviceNode_
+			<< "': " << strerror(-ret);
+		return ret;
+	}
+	fd_ = ret;
+
+	return 0;
+}
+
+/**
+ * \brief Check if the subdevice is open
+ * \return True if the subdevice is open, false otherwise
+ */
+bool V4L2Subdevice::isOpen() const
+{
+	return fd_ != -1;
+}
+
+/**
+ * \brief Close the subdevice, releasing any resources acquired by open()
+ */
+void V4L2Subdevice::close()
+{
+	if (!isOpen())
+		return;
+
+	::close(fd_);
+	fd_ = -1;
+}
+
+/**
+ * \fn V4L2Subdevice::deviceNode()
+ * \brief Retrieve the path of the device node associated with the subdevice
+ *
+ * \return The subdevice's device node system path
+ */
+
+/**
+ * \brief Set a crop rectangle on one of the V4L2 subdevice pads
+ * \param[in] pad The 0-indexed pad number the rectangle is to be applied to
+ * \param[inout] rect The rectangle describing crop target area
+ *
+ * \return 0 on success, or a negative error code otherwise
+ */
+int V4L2Subdevice::setCrop(unsigned int pad, Rectangle *rect)
+{
+	return setSelection(pad, V4L2_SEL_TGT_CROP, rect);
+}
+
+/**
+ * \brief Set a compose rectangle on one of the V4L2 subdevice pads
+ * \param[in] pad The 0-indexed pad number the rectangle is to be applied to
+ * \param[inout] rect The rectangle describing the compose target area
+ *
+ * \return 0 on success, or a negative error code otherwise
+ */
+int V4L2Subdevice::setCompose(unsigned int pad, Rectangle *rect)
+{
+	return setSelection(pad, V4L2_SEL_TGT_COMPOSE, rect);
+}
+
+/**
+ * \brief Retrieve the image format set on one of the V4L2 subdevice pads
+ * \param[in] pad The 0-indexed pad number the format is to be retrieved from
+ * \param[out] format The image bus format
+ *
+ * \return 0 for success, a negative error code otherwise
+ */
+int V4L2Subdevice::getFormat(unsigned int pad, V4L2SubdeviceFormat *format)
+{
+	struct v4l2_subdev_format subdevFmt = {};
+	subdevFmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
+	subdevFmt.pad = pad;
+
+	int ret = ioctl(fd_, VIDIOC_SUBDEV_G_FMT, &subdevFmt);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2Subdev, Error)
+			<< "Unable to get format on pad " << pad
+			<< " of " << deviceNode_ << ": " << strerror(-ret);
+		return ret;
+	}
+
+	format->width = subdevFmt.format.width;
+	format->height = subdevFmt.format.height;
+	format->mbus_code = subdevFmt.format.code;
+
+	return 0;
+}
+
+/**
+ * \brief Set an image format on one of the V4L2 subdevice pads
+ * \param[in] pad The 0-indexed pad number the format is to be applied to
+ * \param[inout] format The image bus format to apply to the subdevice's pad
+ *
+ * Apply the requested image format to the desired media pad and return the
+ * actually applied format parameters, as \ref V4L2Subdevice::getFormat would
+ * do.
+ *
+ * \return 0 for success, a negative error code otherwise
+ */
+int V4L2Subdevice::setFormat(unsigned int pad, V4L2SubdeviceFormat *format)
+{
+	struct v4l2_subdev_format subdevFmt = {};
+	subdevFmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
+	subdevFmt.pad = pad;
+	subdevFmt.format.width = format->width;
+	subdevFmt.format.height = format->height;
+	subdevFmt.format.code = format->mbus_code;
+
+	int ret = ioctl(fd_, VIDIOC_SUBDEV_S_FMT, &subdevFmt);
+	if (ret) {
+		ret = -errno;
+		LOG(Error) << "Unable to set format: " << strerror(-ret);
+		return ret;
+	}
+
+	format->width = subdevFmt.format.width;
+	format->height = subdevFmt.format.height;
+	format->mbus_code = subdevFmt.format.code;
+
+	return 0;
+}
+
+int V4L2Subdevice::setSelection(unsigned int pad, unsigned int target,
+				Rectangle *rect)
+{
+	struct v4l2_subdev_selection sel = {};
+
+	sel.which = V4L2_SUBDEV_FORMAT_ACTIVE;
+	sel.pad = pad;
+	sel.target = target;
+	sel.flags = 0;
+
+	sel.r.left = rect->y;
+	sel.r.top = rect->x;
+	sel.r.width = rect->w;
+	sel.r.height = rect->h;
+
+	int ret = ioctl(fd_, VIDIOC_SUBDEV_S_SELECTION, sel);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2Subdev, Error)
+			<< "Unable to set rectangle " << target << " on pad "
+			<< pad << " of " << deviceNode_ << ": "
+			<< strerror(-ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+} /* namespace libcamera */