Re: hotplug, input and XFree86

[Stephane Chauveau <s.chauveau@chello.nl>]

Humm... Stupid mailer :-) 
Here is the complete mail:


Hi, 

is there a project to handle hotpluging of X11 input devices?

For example, I have a Wacom USB tablet. Hotplug works well except 
that the input subsystem is not yet integrated so I have to guess 
which  input device number is use by the tablet. 

Even with a proper input subsystem, the X server will have to 
be stopped and restarted when a new device is plugged in :-(

A first approach could be to change XFree86 but I have the 
feeling that I could take months or years.

So I propose to develop a generic 'input' driver for 
XFree86. This input driver will only understand a subset
of the kernel-input events corresponding more or less
to the native X11 events (motions in n-dimensions, 
n-buttons press/release and key press/release).

Those events will not be provided directly by the kernel
drivers by a daemon started before the X server.

The daemon will be responsible for
  - Creating one or more devices (daemon device) for each 
    physical device  that could be plugged in the system 
    Those file devices can be opened by the XFree86 generic 'input' 
    driver even if the physical device is yet not plugged in.
  - respond to hotplug requests by mapping those demon daemon devices
    to the kernel input devices.
  - translate kernel input events to XFree86 input events
    and redirect them to the appropriate daemon device.


Example: For my wacom, the daemon would load a wacom.o
driver and create 3 devices.

/dev/daemon-input/wacom-stylus
/dev/daemon-input/wacom-eraser
/dev/daemon-input/wacom-mouse

consider that the wacom is plugged in /dev/input/event0.

the daemon driver has to interpret the wacom specific event
ABS_PRESSURE, BTN_TOOL_STYLUS, BTN_TOOL_ERASER, ABS_TILTX,
and map them to more standard event. In the XFree wacom driver,
the pressure is on the Z axis so all ABS_PRESSURE events will
be transformed into ABS_Z events. 
The BTN_TOOL_??? events will be used to select the output 
device to use. 

 
From an XFree point of view, all devices have to be
configured in the XF86Config file. 

Example: for the wacom stylus

Section "InputDevice"
        Identifier  "gstylus"
        Driver  "generic-input"
        Option  "Device" "/dev/daemon-input/wacom-stylus"
       
        # my wacom supports only 3 dimensions: X, Y and Pressure
        Option "Dimensions" "3"
        
        Option "Mode0" "absolute"
        Option "Max0"  "10206"

        Option "Mode1" "absolute"
        Option "Max1"  "7422"

        Option "Mode2" "absolute"
        Option "Max2"  "511"

        # and 3 buttons
        Option "Buttons"  "3"

EndSection




  


 


_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel