[libcamera-devel,v3,1/6] libcamera: Add V4L2Controls

1425 diff mbox series

diff --git a/src/libcamera/include/v4l2_controls.h b/src/libcamera/include/v4l2_controls.h
new file mode 100644
index 000000000000..d7b12801329e
--- /dev/null
+++ b/src/libcamera/include/v4l2_controls.h
@@ -0,0 +1,96 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_controls.h - V4L2 Extended Control Support
+ */
+
+#ifndef __LIBCAMERA_V4L2_CONTROLS_H__
+#define __LIBCAMERA_V4L2_CONTROLS_H__
+
+#include <cstring>
+#include <string>
+#include <vector>
+
+#include <stdint.h>
+
+#include <linux/v4l2-controls.h>
+#include <linux/videodev2.h>
+
+namespace libcamera {
+
+class V4L2ControlInfo
+{
+public:
+	V4L2ControlInfo(const struct v4l2_query_ext_ctrl &ctrl);
+
+	unsigned int id() const { return id_; }
+	unsigned int type() const { return type_; }
+	size_t size() const { return size_; }
+	const std::string &name() const { return name_; }
+
+private:
+	unsigned int type_;
+	std::string name_;
+	unsigned int id_;
+	size_t size_;
+};
+
+class V4L2Control
+{
+public:
+	unsigned int id() const { return id_; }
+
+private:
+	friend class V4L2Device;
+	friend class V4L2Controls;
+
+	V4L2Control(unsigned int id)
+		: id_(id) {}
+	V4L2Control(unsigned int id, int value)
+		: id_(id), value_(value) {}
+
+	long int value() const { return value_; }
+	void setValue(long int value) { value_ = value; }
+
+	unsigned int id_;
+	long int value_;
+};
+
+class V4L2Controls
+{
+public:
+	V4L2Controls &operator=(const V4L2Controls &) = delete;
+
+	using iterator = std::vector<V4L2Control>::iterator;
+	using const_iterator = std::vector<V4L2Control>::const_iterator;
+
+	iterator begin() { return controls_.begin(); }
+	const_iterator begin() const { return controls_.begin(); }
+	iterator end() { return controls_.end(); }
+	const_iterator end() const { return controls_.end(); }
+
+	bool empty() const { return controls_.empty(); }
+	size_t size() { return controls_.size(); }
+	void reset() { controls_.clear(); }
+
+	V4L2Control *operator[](unsigned int index)
+	{
+		return &controls_[index];
+	}
+
+	void add(unsigned int id, long int value);
+	void add(unsigned int id);
+
+	int get(unsigned int id);
+	int set(unsigned int id, long int value);
+
+private:
+	V4L2Control *getControl(unsigned int id);
+
+	std::vector<V4L2Control> controls_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_V4L2_CONTROLS_H__ */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index f26ad5b2dc57..985aa7e8ab0e 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -23,6 +23,7 @@  libcamera_sources = files([
     'stream.cpp',
     'timer.cpp',
     'utils.cpp',
+    'v4l2_controls.cpp',
     'v4l2_device.cpp',
     'v4l2_subdevice.cpp',
     'v4l2_videodevice.cpp',
diff --git a/src/libcamera/v4l2_controls.cpp b/src/libcamera/v4l2_controls.cpp
new file mode 100644
index 000000000000..75b9c29ca133
--- /dev/null
+++ b/src/libcamera/v4l2_controls.cpp
@@ -0,0 +1,337 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_controls.cpp - V4L2 Extended Control Support
+ */
+
+#include "v4l2_controls.h"
+
+/**
+ * \file v4l2_controls.h
+ * \brief Support for V4L2 Controls using the V4L2 Extended Controls APIs.
+ *
+ * The V4L2 defined "Control API" allows application to inspect and modify set
+ * of configurable parameters on the video device or subdevice of interest. The
+ * nature of the parameters an application could modify using the control
+ * framework depends on what the driver implements support for, and on the
+ * characteristics of the underlying hardware platform. Generally controls are
+ * used to modify user visible settings, such as the image brightness and
+ * exposure time, or non-standard parameters which cannot be controlled through
+ * the V4L2 format negotiation API.
+ *
+ * Controls are identified by a numerical id, defined by the V4L2 kernel headers
+ * and have an associated type and class. Each control has a 'value', which is
+ * the data that can be modified with a call to  the 'V4L2Device::setControls()'
+ * operation or retrieved with a call to 'V4L2Device::getControls()'.
+ *
+ * A control class defines the control purpose while its type (along with the
+ * control's flags) defines the type of the control's value content. Controls
+ * might transport a single data value stored in variable inside the control, or
+ * they might as well deal with more complex data types, such as arrays of
+ * matrices, stored in a contiguous memory locations associated with the control
+ * and called 'the payload'. Such controls are called 'compound controls' and
+ * are currently not supported by the Libcamera V4L2 control framework.
+ *
+ * \todo Add support for compound controls
+ *
+ * Libcamera implements support for control using the V4L2 'Extended Control'
+ * framework, which allows easier future handling of controls with payloads
+ * of arbitrary sizes.
+ *
+ * The Libcamera V4L2 Controls framework operates on lists of controls, wrapped
+ * by the V4L2Controls class, to match the V4L2 extended controls framework.
+ * The interface to set and get control is implemented by the V4L2Device class,
+ * and this file only provides the data type definitions.
+ */
+
+namespace libcamera {
+
+/**
+ * \class V4L2ControlInfo
+ * \brief Information on a V4L2 control
+ *
+ * The V4L2ControlInfo class represent all the informations relative to
+ * a V4L2 control, such as its id, its type, its user-readable name and the
+ * expected size of its value data.
+ *
+ * V4L2ControlInfo instances are created by inspecting the field of
+ * a struct v4l2_query_ext_ctrl structure, after it has been filled by the
+ * device driver as a consequence of an VIDIOC_QUERY_EXT_CTRL ioctl call.
+ *
+ * This class does not contain the control value, but only static informations
+ * on the control, which should ideally be cached the first time the control
+ * is accessed to be reused each time the control value need to be read or
+ * applied to the hardware.
+ */
+
+/**
+ * \brief Construct a V4L2ControlInfo from a struct v4l2_query_ext_ctrl
+ */
+V4L2ControlInfo::V4L2ControlInfo(const struct v4l2_query_ext_ctrl &ctrl)
+{
+	id_ = ctrl.id;
+	type_ = ctrl.type;
+	name_ = static_cast<const char *>(ctrl.name);
+	size_ = ctrl.elem_size * ctrl.elems;
+}
+
+/**
+ * \fn V4L2ControlInfo::id()
+ * \brief Retrieve the control id this instance refers to
+ * \return The V4L2 control id
+ */
+
+/**
+ * \fn V4L2ControlInfo::type()
+ * \brief Retrieve the control type as defined by V4L2_CTRL_TYPE_
+ * \return The V4L2 control type
+ */
+
+/**
+ * \fn V4L2ControlInfo::size()
+ * \brief Retrieve the control value data size (in bytes)
+ * \return The V4L2 control value data size
+ */
+
+/**
+ * \fn V4L2ControlInfo::name()
+ * \brief Retrieve the control user readable name
+ * \return The V4L2 control user readable name
+ */
+
+/**
+ * \class V4L2Control
+ * \brief A V4L2 control value
+ *
+ * The V4L2Control class represent the value of a V4L2 control.
+ * The class stores values that have been read from or will be applied to
+ * a V4L2 device.
+ *
+ * The value stored in the class instances does not reflect what is actually
+ * applied to the hardware but is a pure software cache optionally initialized
+ * at control creation time and only modified by a control read operation or a
+ * call to V4L2Controls::set().
+ *
+ * The V4L2Control class instances are not meant to be directly used but are
+ * instead intended to be grouped in V4L2Controls instances, which are then
+ * passed as parameters to the set and get control operations implemented in
+ * V4L2Device::setControls() and V4L2Device::setControls() respectively.
+ *
+ * In facts, access to the class constructor and to the control value accessor
+ * and modifier are restricted to the friend V4L2Controls and V4L2Device
+ * classes.
+ */
+
+/**
+ * \fn V4L2Control::id()
+ * \brief Retrieve the control id this instance refers to
+ * \return The V4L2Control id
+ */
+
+/**
+ * \class V4L2Controls
+ * \brief Wraps a list of V4L2Control
+ *
+ * The V4L2Controls class works as a wrapper for a list of V4L2Control
+ * instances. The class provides operations to add a new control to the list,
+ * get back a control value, and reset the list of controls it contains.
+ *
+ * In order to set and get controls, user of the Libcamera V4L2 control
+ * framework should operate on instances of the V4L2Controls class, and use
+ * them as argument for the V4L2Device::setControls() and
+ * V4L2Device::getControls() operations, which write and read a list of
+ * controls from or to a V4L2 device (a video device or a subdevice).
+ *
+ * Controls are added to a V4L2Controls instance with the add() method, with
+ * or without an initial value.
+ *
+ * To write controls to a device, the controls of interest should be added
+ * with an initial value by calling V4L2Controls::add(unsigned int id, long
+ * int value) to prepare for a write operation. The value of controls which
+ * are already part of the instance could be updated with a call to
+ * V4L2Controls::set() operation. Once the values of all controls of interest
+ * have been initialized in a V4L2Controls instance, this should be then
+ * passed to the V4L2Device::setControls() operation, which applies each
+ * control in the list to the hardware.
+ *
+ * Alternatively a control can be add without any initial value by calling
+ * V4L2Controls::add(unsigned int id) and then read from the device passing
+ * the V4L2Controls instance to V4L2Device::getControls() which read each
+ * control value from the hardware.
+ *
+ * Reading controls with an initialized value from the device, overwrites the
+ * control's value, reflecting what has been actually read from the hardware.
+ *
+ * V4L2Controls instances can be reset to remove all controls it contains and
+ * prepare to be re-used for a new control write/read sequence. Alternatively,
+ * the value of a control already part of the instance could be updated by using
+ * the V4L2Controls::set() method, to avoid going through a reset() when a
+ * control has to be read then written to the hardware in sequence.
+ *
+ * In facts, the following pseudo-code sequences lead to the same result:
+ *
+ * V4L2Controls controls;
+ * controls.add(V4L2_CID_xx);
+ * dev->getControls(&controls);
+ * controls.set(V4L2_CID_xx, value);
+ * dev->setControls(&controls);
+ *
+ * V4L2Controls controls;
+ * controls.add(V4L2_CID_xx);
+ * dev->getControls(&controls);
+ * controls.reset();
+ * controls.add(V4L2_CID_xx, value);
+ * dev->setControls(&controls);
+ */
+
+/**
+ * \typedef V4L2Controls::iterator
+ * \brief Iterator on the V4L2 controls contained in the instance
+ */
+
+/**
+ * \typedef V4L2Controls::const_iterator
+ * \brief Const iterator on the  V4L2 controls contained in the instance
+ */
+
+/**
+ * \fn iterator V4L2Controls::begin()
+ * \brief Retrieve an iterator to the first V4L2Control in the instance
+ * \return An iterator to the first V4L2 control
+ */
+
+/**
+ * \fn const_iterator V4L2Controls::begin() const
+ * \brief Retrieve a constant iterator to the first V4L2Control in the instance
+ * \return A constant iterator to the first V4L2 control
+ */
+
+/**
+ * \fn iterator V4L2Controls::end()
+ * \brief Retrieve an iterator pointing to the past-the-end V4L2Control in the
+ * instance
+ * \return An iterator to the element following the last V4L2 control in the
+ * instance
+ */
+
+/**
+ * \fn const_iterator V4L2Controls::end() const
+ * \brief Retrieve a constant iterator pointing to the past-the-end V4L2Control
+ * in the instance
+ * \return A constant iterator to the element following the last V4L2 control
+ * in the instance
+ */
+
+/**
+ * \fn V4L2Controls::empty()
+ * \brief Verify if the instance does not contain any control
+ * \return True if the instance does not contain any control, false otherwise
+ */
+
+/**
+ * \fn V4L2Controls::size()
+ * \brief Retrieve the number on controls in the instance
+ * \return The number of V4L2Control stored in the instance
+ */
+
+/**
+ * \fn V4L2Controls::reset()
+ * \brief Removes all controls in the instance
+ */
+
+/**
+ * \fn V4L2Controls::operator[](unsigned int index)
+ * \brief Access the control at index \a index
+ * \param index The index to access
+ */
+
+/**
+ * \brief Add control \a id with a \a value to the instance
+ * \param id The V4L2 control id (V4L2_CID_xx)
+ * \param value The V4L2 control value
+ */
+void V4L2Controls::add(unsigned int id, long int value)
+{
+	/* Cannot use emplace_back() as the V4L2Control ctor is private. */
+	V4L2Control ctrl(id, value);
+	controls_.push_back(ctrl);
+}
+
+/**
+ * \brief Add control \a id without an initial value  to the instance
+ * \param id The V4L2 control id (V4L2_CID_xx)
+ */
+void V4L2Controls::add(unsigned int id)
+{
+	/* Cannot use emplace_back() as the V4L2Control ctor is private. */
+	V4L2Control ctrl(id);
+	controls_.push_back(ctrl);
+}
+
+/**
+ * \brief Retrieve the value of the control with \a id
+ * \param id The V4L2 control id (V4L2_CID_xx)
+ *
+ * Retrieve the value of the control with id \a id.
+ *
+ * It is important to notice that the returned value is not read from the
+ * hardware at the time this operation is called, but it's the cached value
+ * obtained the most recent time the control has been read with
+ * V4L2Device::getControls() or the value of the control has been set to by the
+ * user with the add() or set() operation.
+ *
+ * \return The V4L2 control value or a negative error code if the control id
+ * is not part of this instance
+ */
+int V4L2Controls::get(unsigned int id)
+{
+	V4L2Control *ctrl = getControl(id);
+	if (!ctrl)
+		return -EINVAL;
+
+	return ctrl->value();
+}
+
+/**
+ * \brief Set the value of the control with \a id
+ * \param id The V4L2 control id (V4L2_CID_xx)
+ * \param value The new V4L2 control value
+ *
+ * Set the value of the control with id \a id.
+ *
+ * It is important to notice that the value is not applied to the
+ * hardware at the time this operation is called, but it will only
+ * be actually pplied only by calling V4L2Device::setControls().
+ *
+ * \return 0 on success or a negative error code if the control id
+ * is not part of this instance
+ */
+int V4L2Controls::set(unsigned int id, long int value)
+{
+	V4L2Control *ctrl = getControl(id);
+	if (!ctrl)
+		return -EINVAL;
+
+	ctrl->setValue(value);
+
+	return 0;
+}
+
+/*
+ * \brief Get a pointer the control with \a id
+ * \param id The V4L2 control id (V4L2_CID_xx)
+ * \return A pointer to the V4L2Control with id \a id or nullptr  if the
+ * control id is not part of this instance.
+ */
+V4L2Control *V4L2Controls::getControl(unsigned int id)
+{
+	for (V4L2Control &ctrl : controls_) {
+		if (ctrl.id() == id)
+			return &ctrl;
+	}
+
+	return nullptr;
+}
+
+} /* namespace libcamera */