linux-kernel - Re: [PATCH] Input: i8042 - add quirk for Lenovo ThinkPad T14 Gen 1

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Message-ID: <CALNJtpWr0h+r3=R2scxyCGzgbZ1C6FiYrCGWW1_aSVPBdmNc3Q@mail.gmail.com>
Date: Wed, 10 Jan 2024 17:42:13 -0600
From: Jonathan Denose <jdenose@...omium.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org, Jonathan Denose <jdenose@...gle.com>, 
	Hans de Goede <hdegoede@...hat.com>, Huacai Chen <chenhuacai@...nel.org>, 
	Mattijs Korpershoek <mkorpershoek@...libre.com>, Takashi Iwai <tiwai@...e.de>, 
	Werner Sembach <wse@...edocomputers.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: i8042 - add quirk for Lenovo ThinkPad T14 Gen 1

Dmitry,

Sorry I forgot to reply all, so I'm resending my other email.

On Tue, Jan 9, 2024 at 1:28 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> Hi Jonathan,
>
> On Mon, Nov 27, 2023 at 10:38:57AM -0600, Jonathan Denose wrote:
> > Hi Dmitry
> >
> > On Fri, Nov 24, 2023 at 10:45 PM Dmitry Torokhov
> > <dmitry.torokhov@...il.com> wrote:
> > >
> > > Hi Jonathan,
> > >
> > > On Mon, Sep 25, 2023 at 04:33:20PM -0500, Jonathan Denose wrote:
> > > > The ThinkPad T14 Gen 1 touchpad works fine except that clicking
> > > > and dragging by tapping the touchpad or depressing the touchpad
> > > > do not work. Disabling PNP for controller setting discovery enables
> > > > click and drag without negatively impacting other touchpad features.
> > >
> > > I would like to understand more on how enabling PnP discovery for i8042
> > > affects the touchpad. Do you see it using different interrupt or IO
> > > ports? What protocol does the touchpad use with/without PnP? If the
> > > protocol is the same, do you see difference in the ranges (pressure,
> > > etc) reported by the device?
> > >
> > > Thanks.
> > >
> > > --
> > > Dmitry
> >
> > Without PnP discovery the touchpad is using the SynPS/2 protocol, with
> > PnP discovery, the touchpad is using the rmi4 protocol. Since the
> > protocols are different, so are the ranges but let me know if you
> > still want to see them.
>
> Thank you for this information. So it is not PnP discovery that appears
> harmful in your case, but rather that legacy PS/2 mode appears to be
> working better than RMI4 for the device in question.
>
> I will note that the original enablement of RMI4 for T14 was done by
> Hans in [1]. Later T14 with AMD were added to the list of devices that
> should use RMI4 [2], however this was reverted in [3].
>
> Could you please tell me what exact device you are dealing with? What's
> it ACPI ID?
>
> [1] https://lore.kernel.org/all/20201005114919.371592-1-hdegoede@redhat.com/
> [2] https://lore.kernel.org/r/20220318113949.32722-1-snafu109@gmail.com
> [3] https://lore.kernel.org/r/20220920193936.8709-1-markpearson@lenovo.com
>
> Thanks.
>
> --
> Dmitry

Thanks for your reply!

I'm not 100% sure which of these is the ACPI ID, but from `udevadm
info -e` there's:
N: Name="Synaptics TM3471-020"
P: Phys=rmi4-00/input0