linux-kernel - Re: [PATCH v1] xen/input: add multi-touch support

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Date:   Fri, 30 Jun 2017 10:41:08 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        joculator@...il.com, al1img@...il.com, vlad.babchuk@...il.com,
        andrii.anisov@...il.com, olekstysh@...il.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH v1] xen/input: add multi-touch support

Hi, Dmitry!

On 06/29/2017 10:24 PM, Dmitry Torokhov wrote:
> On June 29, 2017 11:40:30 AM PDT, Oleksandr Andrushchenko <andr2000@...il.com> wrote:
>> Hi, Dmitry!
>>
>> First of all thank you for both the comments and the patch
>>
>> On 06/29/2017 11:17 AM, Dmitry Torokhov wrote:
>>> Hi Oleksandr,
>>>
>>> On Fri, Jun 23, 2017 at 09:09:55AM +0300, Oleksandr Andrushchenko
>> wrote:
>>>> +			switch (event->mtouch.event_type) {
>>>> +			case XENKBD_MT_EV_DOWN:
>>>> +				input_mt_report_slot_state(dev, MT_TOOL_FINGER,
>>>> +							   true);
>>>> +				input_event(dev, EV_ABS, ABS_MT_POSITION_X,
>>>> +					    event->mtouch.u.pos.abs_x);
>>>> +				input_event(dev, EV_ABS, ABS_MT_POSITION_Y,
>>>> +					    event->mtouch.u.pos.abs_y);
>>>> +				input_event(dev, EV_ABS, ABS_X,
>>>> +					    event->mtouch.u.pos.abs_x);
>>>> +				input_event(dev, EV_ABS, ABS_Y,
>>>> +					    event->mtouch.u.pos.abs_y);
>>> I was looking at this and realized that this breaks the single touch
>>> emulation for MT interface: for ST you are supposed to report the
>> oldest
>>> contact, here you report data for all of them. Luckily
>>> input_mt_report_pointer_emulation() that is called as part of
>>> input_mt_sync_frame() reports the correct ABS_X/ABS_Y data and fixes
>>> that for you.
>>>
>>> We should simply remove reporting ABS_X/ABS_Y here and in
>>> XENKBD_MT_EV_MOTION as well.
>>>
>>>> +
>>>> +		input_set_capability(mtouch, EV_KEY, BTN_TOUCH);
>>>> +		input_set_abs_params(mtouch, ABS_X,
>>>> +				     0, width, 0, 0);
>>>> +		input_set_abs_params(mtouch, ABS_Y,
>>>> +				     0, height, 0, 0);
>>>> +		input_set_abs_params(mtouch, ABS_PRESSURE,
>>>> +				     0, 255, 0, 0);
>>> This is done automatically by input_mt_init_slots() when called with
>>> INPUT_MT_DIRECT (as in your case) or INPUT_MT_POINTER, so this can be
>>> removed as well.
>> Great, I was not actually convinced that ABS is really needed
>> to be put here while dealing with MT devices,
>> so the above can be removed
>>> Does the patch below (on top of yours) work for you?
>> Unfortunately I didn't have time to test the patch today, but will try
>> to do so tomorrow.
>>
>> Beside that, do you think that the removals above should go into my
>> patch
>> and the rest of yours (it looks like needed refactoring to me) should
>> go
>> into
>> a separate one, not named "MT support fixups", but rather "Xen input
>> driver refactoring"? Because part of the changes seems to be MT
>> relevant
>> and part is pure refactoring.
>> If so, do you want me to rework your patch with these changes and add
>> on
>> top of mine (I will put your signed off) or you will handle it on your
>> own?
> I was planning on simply folding my changes into your patch and calling it a day, unless your testing would show there is an issue.
I found no issue with the patches, but I have only tested that
on ARM with our new kbd/ptr/mt backend [1]. I am not able to test that
on x86 unfortunately, thus cannot confirm QEMU's backend is ok as well.
What will be the next steps on my side to get MT in?
>   It wasn't intended to be a separate patch in it's own right, I simply sent it out this way to show what exactly I was changing.
>
>
> Thanks.
>
Thank you,
Oleksandr

[1] https://github.com/xen-troops/displ_be