linux-kernel - Re: [PATCH] Revert "Input: clear BTN

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Message-ID: <YkZ+Sie9ANR0r12B@google.com>
Date:   Thu, 31 Mar 2022 21:23:38 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Peter Hutterer <peter.hutterer@...-t.net>
Cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        José Expósito <jose.exposito89@...il.com>,
        Jiri Kosina <jkosina@...e.cz>, Takashi Iwai <tiwai@...e.de>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        "3.8+" <stable@...r.kernel.org>, regressions@...ts.linux.dev,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "Input: clear BTN_RIGHT/MIDDLE on buttonpads"

On Thu, Mar 31, 2022 at 02:38:28PM +1000, Peter Hutterer wrote:
> On Wed, Mar 30, 2022 at 09:13:30PM -0700, Dmitry Torokhov wrote:
> > On Wed, Mar 30, 2022 at 02:30:37PM +0200, Benjamin Tissoires wrote:
> > > On Wed, Mar 30, 2022 at 2:27 PM Thorsten Leemhuis
> > > <regressions@...mhuis.info> wrote:
> > > >
> > > > Hi, this is your Linux kernel regression tracker.
> > > >
> > > > On 21.03.22 19:44, José Expósito wrote:
> > > > > This reverts commit 37ef4c19b4c659926ce65a7ac709ceaefb211c40.
> > > > >
> > > > > The touchpad present in the Dell Precision 7550 and 7750 laptops
> > > > > reports a HID_DG_BUTTONTYPE of type MT_BUTTONTYPE_CLICKPAD. However,
> > > > > the device is not a clickpad, it is a touchpad with physical buttons.
> > > > >
> > > > > In order to fix this issue, a quirk for the device was introduced in
> > > > > libinput [1] [2] to disable the INPUT_PROP_BUTTONPAD property:
> > > > >
> > > > >       [Precision 7x50 Touchpad]
> > > > >       MatchBus=i2c
> > > > >       MatchUdevType=touchpad
> > > > >       MatchDMIModalias=dmi:*svnDellInc.:pnPrecision7?50*
> > > > >       AttrInputPropDisable=INPUT_PROP_BUTTONPAD
> > > > >
> > > > > However, because of the change introduced in 37ef4c19b4 ("Input: clear
> > > > > BTN_RIGHT/MIDDLE on buttonpads") the BTN_RIGHT key bit is not mapped
> > > > > anymore breaking the device right click button and making impossible to
> > > > > workaround it in user space.
> > > > >
> > > > > In order to avoid breakage on other present or future devices, revert
> > > > > the patch causing the issue.
> > > > >
> > > > > Cc: stable@...r.kernel.org
> > > > > Link: https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/481 [1]
> > > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1868789  [2]
> > > > > Signed-off-by: José Expósito <jose.exposito89@...il.com>
> > > > > [...]
> > > >
> > > > Jiri, Benjamin, what the status here? Sure, this is not a crucial
> > > > regression and we are in the middle of the merge window, but it looks
> > > > like nothing has happened for a week now. Or was progress made somewhere
> > > > and I just missed it?
> > > 
> > > No, I think it just wasn't picked up by the input maintainer yet
> > > (Dmitry, now in CC).
> > > 
> > > FWIW:
> > > Acked-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > > 
> > > José, please do not forget to add the input maintainer when you target
> > > the input tree, not the HID one :)
> > 
> > I see that there were several ACKs, but how many devices misuse the
> > HID_DG_BUTTONTYPE? Would it be better to quirk against either affected
> > Dell models, or particular touchpads (by HID IDs) instead of reverting
> > wholesale?
> 
> fwiw, a quick git grep in libinput shows 12 entries for disabling BTN_RIGHT
> and 9 entries for enabling/disabling INPUT_PROP_BUTTONPAD. That's not the
> number of devices affected by this bug, merely devices we know advertise the
> wrong combination.
> 
> Note that the cause for the revert is loss of functionality. Previously, a
> device was just advertising buttons incorrectly but still worked fine. This
> was mostly a cosmetic issue (and could be worked around in userspace). With
> the patch in place some devices right button no longer works because it's
> filtered by the kernel. That's why the revert is needed.
> 
> The device could/should still be quirked to drop INPUT_PROP_BUTTONPAD but that
> is only required to work around the cosmetic issues then.

OK, fair enough, applied.

Thank you.

-- 
Dmitry