linux-kernel - Re: [PATCH v3 3/9] input: elants: remove unused axes

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Date:   Sun, 26 Apr 2020 18:39:41 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Henrik Rydberg <rydberg@...math.org>,
        James Chen <james.chen@....com.tw>,
        Johnny Chuang <johnny.chuang@....com.tw>,
        Rob Herring <robh+dt@...nel.org>,
        Scott Liu <scott.liu@....com.tw>,
        David Heidelberg <david@...t.cz>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/9] input: elants: remove unused axes

26.04.2020 14:21, Michał Mirosław пишет:
> On Sat, Apr 25, 2020 at 09:52:00PM -0700, Dmitry Torokhov wrote:
>> On Mon, Apr 13, 2020 at 03:32:23PM +0200, Michał Mirosław wrote:
>>> Driver only ever reports MT events. Clear capabilities of all others.
>> This is not true. input_mt_sync_frame() calls
>> input_mt_report_pointer_emulation() which does emut single-touch events
>> for the benefit of older userspace (or userspace that is not interested
>> in multitouch).
> 
> Oh, I didn't notice that. Looking at the code, I see that
> input_mt_init_slots() sets up the emulated axes in this case.
> 
> Do you need me to update the commitmsg?

I tried Ubuntu 12.04 that uses ancient libinput (or whatever it was back
then), which doesn't support MT. Mouse doesn't move at all with this
patch being applied. Without this patch mouse moves, but it's not usable
because the cursor's position is wrong, i.e. mouse position doesn't
match the screen touches.

This means that input_mt_report_pointer_emulation() doesn't set up
everything needed for the legacy pointer emulation.