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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2019, Google Inc.
*
* v4l2_controls.cpp - V4L2 Controls Support
*/
#include "v4l2_controls.h"
#include <string.h>
/**
* \file v4l2_controls.h
* \brief Support for V4L2 Controls using the V4L2 Extended Controls APIs
*
* The V4L2 Control API allows application to inspect and modify sets of
* configurable parameters on a video device or subdevice. The nature of the
* parameters an application can 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. Each control has a value, which is the data that
* can be modified with V4L2Device::setControls() or retrieved with
* V4L2Device::getControls().
*
* The control's type along with the control's flags define the type of the
* control's value content. Controls can 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.
*
* libcamera implements support for controls using the V4L2 Extended Control
* API, which allows future handling of controls with payloads of arbitrary
* sizes.
*
* The libcamera V4L2 Controls framework operates on lists of controls, wrapped
* by the ControlList class, to match the V4L2 extended controls API. The
* interface to set and get control is implemented by the V4L2Device class, and
* this file only provides the data type definitions.
*
* \todo Add support for compound controls
*/
namespace libcamera {
namespace {
std::string v4l2_ctrl_name(const struct v4l2_query_ext_ctrl &ctrl)
{
size_t len = strnlen(ctrl.name, sizeof(ctrl.name));
return std::string(static_cast<const char *>(ctrl.name), len);
}
ControlType v4l2_ctrl_type(const struct v4l2_query_ext_ctrl &ctrl)
{
switch (ctrl.type) {
case V4L2_CTRL_TYPE_BOOLEAN:
return ControlTypeBool;
case V4L2_CTRL_TYPE_INTEGER:
return ControlTypeInteger32;
case V4L2_CTRL_TYPE_INTEGER64:
return ControlTypeInteger64;
case V4L2_CTRL_TYPE_MENU:
case V4L2_CTRL_TYPE_BUTTON:
case V4L2_CTRL_TYPE_BITMASK:
case V4L2_CTRL_TYPE_INTEGER_MENU:
/*
* More precise types may be needed, for now use a 32-bit
* integer type.
*/
return ControlTypeInteger32;
default:
return ControlTypeNone;
}
}
} /* namespace */
/**
* \class V4L2ControlId
* \brief V4L2 control static metadata
*
* The V4L2ControlId class is a specialisation of the ControlId for V4L2
* controls.
*/
/**
* \brief Construct a V4L2ControlId from a struct v4l2_query_ext_ctrl
* \param[in] ctrl The struct v4l2_query_ext_ctrl as returned by the kernel
*/
V4L2ControlId::V4L2ControlId(const struct v4l2_query_ext_ctrl &ctrl)
: ControlId(ctrl.id, v4l2_ctrl_name(ctrl), v4l2_ctrl_type(ctrl))
{
}
/**
* \class V4L2ControlRange
* \brief Convenience specialisation of ControlRange for V4L2 controls
*
* The V4L2ControlRange class is a specialisation of the ControlRange for V4L2
* controls. It offers a convenience constructor from a struct
* v4l2_query_ext_ctrl, and is otherwise equivalent to the ControlRange class.
*/
/**
* \brief Construct a V4L2ControlRange from a struct v4l2_query_ext_ctrl
* \param[in] ctrl The struct v4l2_query_ext_ctrl as returned by the kernel
*/
V4L2ControlRange::V4L2ControlRange(const struct v4l2_query_ext_ctrl &ctrl)
{
if (ctrl.type == V4L2_CTRL_TYPE_INTEGER64)
ControlRange::operator=(ControlRange(static_cast<int64_t>(ctrl.minimum),
static_cast<int64_t>(ctrl.maximum)));
else
ControlRange::operator=(ControlRange(static_cast<int32_t>(ctrl.minimum),
static_cast<int32_t>(ctrl.maximum)));
}
} /* namespace libcamera */
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