Weston 1.8.0: touch input using evdev not working

Benjamin Tissoires benjamin.tissoires at gmail.com
Fri Sep 25 04:18:02 PDT 2015

On Fri, Sep 25, 2015 at 2:22 AM, Vikas Patil <vikasmpatil at gmail.com> wrote:
> Dear Members,
> I am trying Weston 1.8.0 on i.MX6 with Freescale linux 3.14.28 and seems
> that touch input is not working for me. Weston.log show the following
> messages. I am not using llibinput backend yet.

That's weird. Since Weston 1.7.0, there are no other backend than
libinput for handling input devices. Or maybe I am missing something?

> Could anyone give some inputs/suggestion to fix this? Is this due to
> following ckeck-in?
> http://lists.freedesktop.org/archives/wayland-devel/2015-June/022411.html

Yes it is, but believe me, it is for the better. Your touchscreen is
not properly tagged by udev, so we need to fix the kernel to make it
look like a touchscreen that libinput could understand.

> [00:00:50.248] input device 'mxt540e_i2c', /dev/input/event0 not tagged as
> input
> [00:00:50.248] failed to create input device '/dev/input/event0'.
> [00:00:50.249] warning: no input devices on entering Weston. Possible
> causes:
>         - no permissions to read /dev/input/event*
>         - seats misconfigured (Weston backend option 'seat', udev device
> propert
> I can see “/dev/input/event0” already there and all the touch drivers and
> dependencies (i.e. mxt540e.ko, input_polldev.ko, evdev.ko) are loaded.
> root at linux:~# udevadm info /dev/input/event0
> P: /devices/virtual/input/input0/event0
> N: input/event0
> E: DEVNAME=/dev/input/event0
> E: DEVPATH=/devices/virtual/input/input0/event0
> E: MAJOR=13
> E: MINOR=64
> E: SUBSYSTEM=input

You are missing all the important bits here. For instance, on my
touchscreen I have:
$ sudo udevadm info /dev/input/event6
P: /devices/pci0000:00/INT3433:00/i2c-8/i2c-ATML0001:01/input/input6/event6
N: input/event6
S: input/by-path/platform-INT3433:00-event
E: DEVLINKS=/dev/input/by-path/platform-INT3433:00-event
E: DEVNAME=/dev/input/event6
E: DEVPATH=/devices/pci0000:00/INT3433:00/i2c-8/i2c-ATML0001:01/input/input6/event6
E: EVDEV_ABS_00=::10
E: EVDEV_ABS_01=::10
E: EVDEV_ABS_35=::10
E: EVDEV_ABS_36=::10
E: ID_PATH=platform-INT3433:00
E: ID_PATH_TAG=platform-INT3433_00
E: LIBINPUT_DEVICE_GROUP=18/0/0/0:i2c-8-004b

The device is tagged with ID_INPUT_TOUCHSCREEN which makes libinput handling it.

Could you attach an evemu-record of your touchscreen that we
understand why udev ignores it?


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