Re: Mixed "pen" and multitouch input devices

[Chase Douglas <chasedouglas@gmail.com>]

On 03/15/2012 10:56 AM, Thorsten Wissmann wrote:
> On Thu, Mar 15, 2012 at 12:27:22PM -0500, Chris Bagwell wrote:
>> Its also true that sharing ABS_X/Y events between both a BTN_TOOL_PEN
>> and a BTN_TOOL_FINGER will confuse most user land apps (they think
>> only touchpads can declare BTN_TOOL_FINGER's but this is a
>> touchscreen) and it also has bad side affects to the kernel's MT
>> pointer emulation functions.
>>
>> You can look at kernel drivers/input/touchscreen/wacom_w8001.c for an
>> example touchscreen that supports pen and at least 2 MT touches on a
>> single /dev/input device (because HW packets come over single serial
>> interface).  It does not declare a BTN_TOOL_FINGER nor use pointer
>> emulation to overcome issues I mentioned and xf86-input-wacom
>> understands how to handle this device.
>>
>> If you want to work with other unmodified user land apps (perhaps
>> xf86-input-evdev for touches) then its probably easiest to split pen
>> and touch to separate input devices.  drivers/input/tablet/wacom_wac.c
>> shows some examples of that approach but that driver doesn't have to
>> work to hard to split in to 2 input devices because the USB device
>> already puts the events on separate USB  interfaces.
> 
> OK. We want the device to work with the xf86-input-evdev driver. So we
> will split it into two devices.

Or you could teach evdev to know how to handle mixed devices :). I think
that's the "better" approach over all, but it's up to you.

-- Chase