[Gta04-owner] Using touchscreen as a touchpad?

H. Nikolaus Schaller hns at goldelico.com
Sat Apr 23 08:00:30 CEST 2016


> Am 23.04.2016 um 01:19 schrieb Neil Jerram <neil at ossau.homelinux.net>:
> 
> On 22/04/16 12:00, Neil Jerram wrote:
>> On 21/04/16 20:04, Neil Jerram wrote:
>>> On 21/04/16 13:08, Neil Jerram wrote:
>>>> Has anyone tried configuring the GTA04 touchscreen to behave as a
>>>> touchpad instead of a touchscreen?  Would the kernel code for the
>>>> touchscreen support that?
>>>> 
>>>> Subject to the latter, I think the former is possible in principle by
>>>> using libinput and configuring a udev rule like this:
>>>> 
>>>> ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="...",
>>>> ENV{ID_MODEL_ID}=="...b", ENV{ID_INPUT_TOUCHSCREEN}="",
>>>> ENV{ID_INPUT_TOUCHPAD}="1"
>>> 
>>> Well, unfortunately it does not work.  Xorg.0.log says:
>>> 
>>> [    19.473] (II) input device 'TSC2007 Touchscreen', /dev/input/event0 is tagged by udev as: Touchpad Touchscreen
>>> [    19.473] (EE) kernel bug: device TSC2007 Touchscreen failed touchpad sanity checks
>>> [    19.473] (II) input device 'TSC2007 Touchscreen', /dev/input/event0 is a touchpad
>>> [    19.540] (II) failed to create input device '/dev/input/event0'.
>>> 
>>> I guess libinput is expecting some minimal characteristics for a 'touchpad', and the TSC2007 kernel driver doesn't provide those. Pity, because I would like to see if it was usable that way.
>> 
>> Yes, libinput checks for ABS_X, BTN_TOUCH and BTN_TOOL_FINGER. The driver provides ABS_X and BTN_TOUCH but not BTN_TOOL_FINGER.
>> 
>> It looks like a trivial change to get the driver to advertise BTN_TOOL_FINGER, so I plan to try that next.  If it works we could implement a driver option for it, so as to allow either touchscreen or touchpad use.
> 
> Just hit a further problem here: the amd64->armhf cross-compilation toolchain now in Debian is GCC 5,

could you use an older version or are there unmatched dependencies?

> but the kernel back at 3.17 didn't support building with GCC 5.  Is there a much more recent kernel - since whenever the GCC 5 support was added - that more or less runs correctly on the GTA04?

Yes: 

http://projects.goldelico.com/p/gta04-kernel/

It is not feature complete but works well enough for such experiments. You can also try the 4.4 kernel but I would not look into older ones. 4.6-rc* did not boot on the GTA04 (while it boots on OMAP5) during my recent tests, but I haven't looked deeply enough into it. Also something for the hacking weekend...

BR,
Nikolaus



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