linux-kernel - Re: [GIT PULL] HID for 4.11

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Date:   Tue, 28 Feb 2017 18:31:10 -0800
From:   Andrew Duggan <aduggan@...aptics.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Hutterer <peter.hutterer@...-t.net>
Subject: Re: [GIT PULL] HID for 4.11

On 02/28/2017 04:56 PM, Linus Torvalds wrote:
> On Mon, Feb 20, 2017 at 8:37 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>> Yeah, so enabling HID_RMI makes my touchpad work again.
> .. so I just noticed something: it works subtly differently.
>
> When I drag something around, I mostly just double-tap and move, and
> that still works fine.
>
> But sometimes I click (and hold) with one finger, and then move around
> with another. That's occasionally very useful when you move longer
> distances, because you can just raise and move that other finger
> multiple times.
>
> That doesn't seem to work with the RMI driver. I seem to get scroll
> events instead.
>
> I'm sure there's some setting for mouse gestures. But it's a bit odd
> when they change just because the driver changes. And gnome certainly
> doesn't believe in settings, because these things are obviously
> "intuitive".
>
> Ideas? Or am I just dreaming, and the click-and-move never worked?
> Because I'm pretty sure it did, but sometimes the meds kick in.
>
>                   Linus

The RMI driver does report input events a little differently then the 
hid-multitouch driver. It may report different min / max values for 
axis, different resolution values, and it also reports ABS_MT_PRESSURE. 
Also, depending on how the touchpad's firmware was configured it may 
also report additional fingers. It probably also reports a few other 
properties which hid-multitouch does not. Since it is the input handling 
libraries in userspace which interpret the input events and decide what 
is a drag and what is a scroll I suspect the issue may be in userspace. 
The additional properties reported by the input device may be causing 
the input handler to potentially misidentify the device and treat it 
differently. That's at least where I would start looking.

For what it's worth, I'm using libinput and the RMI driver on my 
touchpad. Click and drag works well with libinput's "ClickMethod" 
parameter set to "clickfinger".

Andrew