wdaemon

wdaemon is a daemon to hide physical tablet unplugging. When it was originally written, the X server did not have input device hotplugging support. Input devices added at runtime could thus not be used. wdaemon worked around this by providing a permanent virtual kernel device that looked exactly like the physical tablet to userspace. The X server was then configured to use the wdaemon device. Whenever a physical tablet was plugged in, wdaemon would then forward the events from this device through the virtual device.

Now the X server ''does'' support input device hotplugging. From a technical point of view, wdaemon works exactly as before. From a practical perspective however it works the other way round - it ''disables'' device hotplugging. A device that would otherwise appear and disappear as X input device now looks like a permanent device to X. Thus, run-time settings applied to this device remain permanent.

Note that the virtual device created by wdaemon will still be hotplugged by the X server (if so configured), hence wdaemon provides a two-layer hotplug abstraction.

Getting wdaemon

The git repository is available at git://git.code.sf.net/p/linuxwacom/wdaemon wdaemon can be downloaded, built, and installed with the usual

   git clone git://git.code.sf.net/p/linuxwacom/wdaemon
   cd wdaemon
   ./autogen.sh --prefix=/usr
   make && make install

Configuration

wdaemon requires configuration of udev and X.Org for proper functioning.

udev configuration

wdaemon comes with udev rules files. These should be installed in the udev rules.d directory (usually /lib/udev/rules.d). Three rules files are provided:

• '''60-wacom.rules''': this rule creates a symlink for each tablet model in /dev/input/wacom-tablets/. Example: /dev/input/wacom-tablets/intuos4-6x9.
• '''61-uinput-wacom.rules''': this rule runs a script on the event devices and if the device is a uinput device created by wdaemon, it creates a symlink in /dev/input/uinput-devices/uinput-wacom-...-tablet. It also applies a udev tag named "wdaemon-device"
• '''61-uinput-stddev.rules''': same as 61-uinput-wacom.rules but for non-tablet devices. You can usually ignore this rule

Kernel event device numbers are not guaranteed to stay the same when the device is removed. Thus a symlink can help greatly with permanent configurations to always point to the same device.

static xorg.conf configuration

To add a wdaemon device to a static xorg.conf, use the uinput link as device.

Section "InputDevice"
    Identifier "wdaemon device"
    Driver "wacom"
    Option "Device" "/dev/input/uinput-devices/uinput-wacom-..."
    # add other options here
EndSection

For static configuration, it is necessary that wdaemon is running ''before'' the X server starts up.

xorg.conf.d configuration snippets

wdaemon ships with a configuration examples for xorg.conf.d (X server 1.8 and later). The approach these examples use is:

• disable the wacom driver for all physical wacom tablets
• enable the wacom driver for all wdaemon devices The example xorg.conf.d snippet:

Section "InputClass"
        Identifier "wdaemon ignore all devices"
        MatchProduct "Wacom|WACOM"
        MatchDevicePath "/dev/input/event*"
        Option "Ignore" "on"
EndSection

Section "InputClass"
        Identifier "wdaemon unignore uinput devices"
        # the wdaemon udev rules tag the device
        MatchTag "wdaemon-device"
        Driver "wacom"
        Option "Ignore" "off"
EndSection

As you can see, we use the udev tag assigned by the rules file to disable Ignore, which causes the device to be added again.

For finer-grained matching (e.g. on a specific tablet), adjust the MatchProduct line in the first part accordingly. Once adjusted, the X server will hotplug all devices but the matched ones, hence providing both real hotplugging and wdaemon-style hotplugging.

HAL configuration

wdaemon ships with a configuration example for HAL configuration (X Servers 1.5 to 1.7). The approach used is the same as for the xorg.conf.d snippet above.

Note: See original text at https://github.com/jigpu/linuxwacom-wiki-archive/blob/master/wiki/Wdaemon.md#hal-configuration

<?xml version="1.0" encoding="ISO-8859-1"?>
<deviceinfo version="0.2">
  <device>
    <match key="info.category" contains="input">
      <match key="info.product" contains_outof="Wacom;WALTOP;WACOM">
         <remove key="input.x11_driver" />
      </match>
      <!-- enable wacom driver for all wdaemon devices -->
      <match key="info.product" contains="wdaemon">
        <merge key="input.x11_driver" type="string">wacom</merge>
      </match>
    </match>
  </device>
</deviceinfo>         

Here we rely on wdaemon to prefix all devices names with ''"wdaemon"'' (we can't match on the udev tag with HAL). Again, for finer-grained matching adjust the ''info.product'' line above. Once adjusted, save this file in ''/etc/fdi/hal/policy'' and restart HAL. It is recommended that you check for correct configuration with lshal. If correctly configured, the input.x11_driver is only set to wacom on the wdaemon devices, but not on the physical devices (wdaemon should be running to see this).

A note on xorg.conf.d and HAL configuration

In the case of xorg.conf.d or HAL configuration, we still use the hotplugging facilities of the X server. wdaemon does not need to be running at server startup. The X server will hotplug the virtual devices when wdaemon is started up. The devices added will use a ''/dev/input/eventX'' device path, hence only the ''60-wacom.rules'' udev rule is required for such a configuration. No uinput symlinks are required.

Running wdaemon

In the simplest case, you run wdaemon with the numeric type of the device and the device path to monitor. Note that wdaemon usually needs to run as root for the appropriate permissions. wdaemon -t 56 -p /dev/input/event12 or, to use the udev symlinks instead: wdaemon -t 52 -p /dev/input/wacom-tablets/intuos4-6x9

Tip: The command wdaemon -w lists all device types known to wdaemon

wdaemon also supports a configuration file format. The above command, when used in a configuration file would be device = 56,/dev/input/wacom-tablets/intuso4-6x9

More lines may be added for additional tablets. wdaemon can then be started with the configuration file (and backkgrounded) wdaemon -f -c path/to/config.file

Tip: The command wdaemon -a prints out a configuration file based on all currently plugged in tablets

Emulating unknown and new devices

wdaemon can emulate tablets without the physical tablet being present. To do this, wdaemon must know the properties of each device. Information about most tablets is built into wdaemon but newer devices may not be supported. If wdaemon needs to emulate a new device, it must first gather a device description from this device. To get such a description, use the ''-x'' flag (for "extract").

  wdaemon -x newdevice.desc -p /dev/input/event12

This will save the device description of the device on ''/dev/input/event12'' in the file ''newdevice.desc''. To re-use this description, simply load the device description.

  wdaemon -l newdevice.desc -p /dev/input/event12

This command will re-create the device described by the file and link it to the device at ''/dev/input/event12''. This line may also be specified in the configuration file as description = path/to/newfile.desc,/dev/input/event12

X.Org configuration is not affected if wdaemon does not natively know a device. The above guidelines still apply.

Warning: The symlinks created by '''60-wacom.rules'' are model-specific. New models must be added to the rules file if symlinks are required.