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Date:   Sun, 12 May 2019 22:59:33 +0200
From:   Błażej Szczygieł <>
To:     Peter Hutterer <>
Cc:     Benjamin Tissoires <>,
        Igor Kushnir <>,
        Jiri Kosina <>,
        "open list:HID CORE LAYER" <>,
        lkml <>
Subject: Re: [PATCH] HID: fix A4Tech horizontal scrolling


On 07.05.2019 at 07:01, Peter Hutterer wrote:
> On Fri, May 03, 2019 at 01:59:23PM +0200, Benjamin Tissoires wrote:
>> Hi,
>> On Fri, May 3, 2019 at 11:43 AM Igor Kushnir <> wrote:
>>> Hi Benjamin,
>>> On 5/3/19 10:36 AM, Benjamin Tissoires wrote:
>>>> Hi,
>>>> On Thu, May 2, 2019 at 11:37 PM Błażej Szczygieł <> wrote:
>>>>> Since recent high resolution scrolling changes the A4Tech driver must
>>>>> check for the "REL_WHEEL_HI_RES" usage code.
>>>>> Fixes: 2dc702c991e3774af9d7ce410eef410ca9e2357e (HID: input: use the
>>>>> Resolution Multiplier for high-resolution scrolling)
>>>>> Signed-off-by: Błażej Szczygieł <>
>>>> Thanks for the patch. I do not doubt this fixes the issues, but I
>>>> still wonder if we should not export REL_HWHEEL_HI_RES instead of
>>>> REL_HWHEEL events.
>>> If you mean exporting REL_HWHEEL_HI_RES instead of REL_HWHEEL from
>>> hid-a4tech.c, then it makes sense to me, though I do not know the code
>>> well enough to be certain.
>> Yep, that's what I meant. I am worried that userspace doesn't know
>> well how to deal with a device that mixes the new and old REL_WHEEL
>> events.
> sorry, I'm not sure what you mean here. The new events are always mixed with
> the old ones anyway, and both should be treated as separate event streams.
> The kernel interface to userspace is fairly easy to deal with, it's the rest
> that's a bit of mess.
> [..]
>> OK, thanks both of you for your logs, this is helpful.
>> So just in case I need to come back later, the horizontal wheel is
>> "just" the normal wheel plus a modifier in the report.
>> Anyway, ideally, can we have a v2 of the patch with the 2 changes
>> requested above in the commit message and the introduction of
>> REL_HWHEEL_HI_RES events in addition to REL_HWHEEL?
>> REL_HWHEEL_HI_RES should report `120*value` and we should also keep
>> the reporting of REL_WHEEL as it is currently.
>> Peter, I grepped in the hid code, and it seems hid-cypress.c is having
>> the exact same issue. Sigh.
> yeah, I found that too when grepping through it. seems to be the only other
> one though and we can use Błażej's patch as boilerplate once it's done.

Peter, I also found comparison of "usage->code ==" with "REL_HWHEEL"
and "REL_WHEEL" in hid-lenovo.c, hid-apple.c, hid-ezkey.c, hid-lg.c.
Unfortunatelly, I don't have such devices to test :(


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