libinput: Static device configuration via udev

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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 LIBINPUT_EVENT_DEVICE_ADDED event is generated.

The following udev properties are supported:

LIBINPUT_CALIBRATION_MATRIX

  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:

  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
LIBINPUT_DEVICE_GROUP
  A string identifying the 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.
ID_SEAT
  Assigns the physical seat for this device. See libinput_seat_get_physical_name(). Defaults to "seat0".
ID_INPUT
  If this property is set, the device is considered an input device. Any device with this property missing will be ignored, see Device type assignment via udev.
ID_INPUT_KEYBOARD, ID_INPUT_KEY, ID_INPUT_MOUSE, ID_INPUT_TOUCHPAD, ID_INPUT_TOUCHSCREEN, ID_INPUT_TABLET, ID_INPUT_JOYSTICK, ID_INPUT_ACCELEROMETER
  If any of the above is set, libinput initializes the device as the given type, see Device type assignment via udev. 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.
WL_SEAT
  Assigns the logical seat for this device. See libinput_seat_get_logical_name() context. Defaults to "default".
MOUSE_DPI
  HW resolution and sampling frequency of a relative pointer device. See Normalization of relative motion for details.
MOUSE_WHEEL_CLICK_ANGLE
  The angle in degrees for each click on a mouse wheel. See libinput_pointer_get_axis_source() for details.
POINTINGSTICK_CONST_ACCEL
  A constant (linear) acceleration factor to apply to pointingstick deltas to normalize them.
LIBINPUT_MODEL_*
  This prefix is reserved as private API, do not use. See Model-specific configuration for details.
LIBINPUT_ATTR_*
  This prefix is reserved as private API, do not use. See Model-specific configuration for details.

Below is an example udev rule to assign "seat1" to a device from vendor 0x012a with the model ID of 0x034b.

ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="012a", \
ENV{ID_MODEL_ID}=="034b", ENV{ID_SEAT}="seat1"

# Device type assignment via udev

libinput requires the ID_INPUT property to be set on a device, otherwise the device will be ignored. In addition, one of ID_INPUT_KEYBOARD, ID_INPUT_KEY, ID_INPUT_MOUSE, ID_INPUT_TOUCHPAD, ID_INPUT_TOUCHSCREEN, ID_INPUT_TABLET, ID_INPUT_JOYSTICK, ID_INPUT_ACCELEROMETER 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 ID_INPUT_TOUCHPAD setting and change it into an ID_INPUT_TABLET setting. This rule would apply for a device with the vendor/model ID of 012a/034b.

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"

# Model-specific configuration

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

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.

## Lenovo x220 with touchpad firmware v8.1

The property LIBINPUT_MODEL_LENOVO_X220_TOUCHPAD_FW81 may be set by a user in a local hwdb file. This property designates the touchpad on a Lenovo x220 with a touchpad firmware version 8.1. When this firmware version is installed, the touchpad is imprecise. The touchpad device does not send continuos x/y axis position updates, a behavior also observed on its successor model, the Lenovo x230 which has the same firmware version. If the above property is set, libinput adjusts its behavior to better suit this particular model.

The touchpad firmware version cannot be detected automatically by libinput, local configuration is required to set this property. Refer to the libinput model quirks hwdb for instructions.

This property must not be used for any other purpose, no specific behavior is guaranteed.