/**
@page udev_config Static device configuration via udev

libinput supports some static configuration through udev properties.
These properties are read when the device is initially added
to libinput's device list, i.e. before the @ref
LIBINPUT_EVENT_DEVICE_ADDED event is generated.

The following udev properties are supported:
<dl>
<dt>LIBINPUT_CALIBRATION_MATRIX</dt>
<dd>Sets the calibration matrix, see
libinput_device_config_calibration_get_default_matrix(). If unset,
defaults to the identity matrix.

The udev property is parsed as 6 floating point numbers separated by a
single space each (scanf(3) format "%f %f %f %f %f %f").
The 6 values represent the first two rows of the calibration matrix as
described in libinput_device_config_calibration_set_matrix().

Example values are:
@code
 ENV{LIBINPUT_CALIBRATION_MATRIX}="1 0 0 0 1 0" # default
 ENV{LIBINPUT_CALIBRATION_MATRIX}="0 -1 1 1 0 0" # 90 degree clockwise
 ENV{LIBINPUT_CALIBRATION_MATRIX}="-1 0 1 0 -1 1" # 180 degree clockwise
 ENV{LIBINPUT_CALIBRATION_MATRIX}="0 1 0 -1 0 1" # 270 degree clockwise
 ENV{LIBINPUT_CALIBRATION_MATRIX}="-1 0 1 1 0 0" # reflect along y axis
@endcode
</dd>
<dt>LIBINPUT_DEVICE_GROUP</dt>
<dd>A string identifying the @ref libinput_device_group for this device. Two
devices with the same property value are grouped into the same device group,
the value itself is irrelevant otherwise.
</dd>
<dt>ID_SEAT</dt>
<dd>Assigns the physical seat for this device. See
libinput_seat_get_physical_name(). Defaults to "seat0".</dd>
<dt>ID_INPUT</dt>
<dd>If this property is set, the device is considered an input device. Any
device with this property missing will be ignored, see @ref
udev_device_type.</dt>
</dd>
<dt>ID_INPUT_KEYBOARD, ID_INPUT_KEY, ID_INPUT_MOUSE, ID_INPUT_TOUCHPAD,
ID_INPUT_TOUCHSCREEN, ID_INPUT_TABLET, ID_INPUT_JOYSTICK,
ID_INPUT_ACCELEROMETER</dt>
<dd>If any of the above is set, libinput initializes the device as the given
type, see @ref udev_device_type. Note that for historical reasons more than
one of these may be set at any time, libinput will select only one of these
to determine the device type. To ensure libinput selects the correct device
type, only set one of them.</dd>
<dt>WL_SEAT</dt>
<dd>Assigns the logical seat for this device. See
libinput_seat_get_logical_name()
context. Defaults to "default".</dd>
<dt>MOUSE_DPI</dt>
<dd>HW resolution and sampling frequency of a relative pointer device.
See @ref motion_normalization for details.
</dd>
<dt>MOUSE_WHEEL_CLICK_ANGLE</dt>
<dd>The angle in degrees for each click on a mouse wheel. See
libinput_pointer_get_axis_source() for details.
</dd>
<dt>POINTINGSTICK_CONST_ACCEL</dt>
<dd>A constant (linear) acceleration factor to apply to pointingstick deltas
to normalize them.
<dt>LIBINPUT_MODEL_*</dt>
<dd><b>This prefix is reserved as private API, do not use.</b>. See @ref
model_specific_configuration for details.
</dd>
<dt>LIBINPUT_ATTR_*</dt>
<dd><b>This prefix is reserved as private API, do not use.</b>. See @ref
model_specific_configuration for details.
</dd>
</dl>

Below is an example udev rule to assign "seat1" to a device from vendor
0x012a with the model ID of 0x034b.
@code
ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="012a", \
ENV{ID_MODEL_ID}=="034b", ENV{ID_SEAT}="seat1"
@endcode


@section udev_device_type Device type assignment via udev

libinput requires the <b>ID_INPUT</b> property to be set on a device,
otherwise the device will be ignored. In addition, one of <b>
ID_INPUT_KEYBOARD, ID_INPUT_KEY, ID_INPUT_MOUSE, ID_INPUT_TOUCHPAD,
ID_INPUT_TOUCHSCREEN, ID_INPUT_TABLET, ID_INPUT_JOYSTICK,
ID_INPUT_ACCELEROMETER</b> must be set on the device to determine the
device type. The usual error handling applies within libinput and a device
type label does not guarantee that the device is initialized by libinput.
If a device fails to meet the requirements for a device type (e.g. a keyboard
labelled as touchpad) the device will not be available through libinput.

Only one device type should be set per device at a type, though libinput can
handle some combinations for historical reasons.

Below is an example udev rule  to remove an <b>ID_INPUT_TOUCHPAD</b> setting
and change it into an <b>ID_INPUT_TABLET</b> setting. This rule would apply
for a device with the vendor/model ID of 012a/034b.

@code
ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="012a", \
ENV{ID_MODEL_ID}=="034b", ENV{ID_INPUT_TOUCHPAD}="", ENV{ID_INPUT_TABLET}="1"
@endcode

@section model_specific_configuration Model-specific configuration

libinput reserves the property prefixes <b>LIBINPUT_MODEL_</b> and
<b>LIBINPUT_ATTR_*</b> for model-specific configuration. <b>These prefixes
are reserved as private API, do not use.</b>

The effect of these properties may be to enable or disable certain
features on a specific device or set of devices, to change configuration
defaults or any other reason. The effects of setting these properties, the
format of the property and the value of the property are subject to change
at any time.

*/