linux-kernel - Re: [4.12 regression] Thinkpad X250 Touchpad and Trackpoint not recognized anymore; commit e839ffa: "Input: synaptics

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Message-ID: <20170520173526.GB38800@dtor-ws>
Date:   Sat, 20 May 2017 10:35:26 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Pascal Wichmann <pascal.wichmann@...w.de>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [4.12 regression] Thinkpad X250 Touchpad and Trackpoint not
 recognized anymore; commit e839ffa: "Input: synaptics - add support for
 Intertouch devices"

On Sat, May 20, 2017 at 11:59:50AM +0200, Benjamin Tissoires wrote:
> Hi,
> 
> On May 20 2017 or thereabouts, Pascal Wichmann wrote:
> > > Looks like you running your patched kernel?
> > That's right.
> > 
> > 
> > >>> CONFIG_RMI4_CORE=m
> > >>> CONFIG_RMI4_I2C=m
> > >>> CONFIG_RMI4_SPI=m
> > >>> # CONFIG_RMI4_SMB is not set
> > >
> > > This is your issue I believe.
> > 
> > Indeed, enabling that configuration solves that issue.
> > 
> > However, I think it is quite unintuitive that a module (psmouse) chooses
> > a default mode which requires another driver which is not necessarily
> > included; though it would probably be not a very clean solution to
> > explicitly check that as well.
> > 
> > Is this behaviour, that one module requires another without
> > communicating that clearly, wanted?
> > 
> 
> I can see 3 solutions:
> 1. Have PS2_SMBUS depending on RMI_SMBUS (and ELAN_I2C, and others when
>    required)
> 2. Have PS2_SMBUS selecting RMI_SMBUS (and the others when time comes)
> 3. Changing the default value of synaptics_intertouch to
>    SYNAPTICS_INTERTOUCH_OFF when RMI_SMBUS is not set
> 
> Solution 3. might be interesting because it doesn't prevent users to
> compile the module on the side and is Synaptics only.
> 
> Dmitry, any comments?

I like #3. We might also want to stick a warning into synaptics.c when
we see a device that has intertouch, but RMI_SMBUS is disabled, so we
could nudge users to switch over to RMI.

Thanks.

-- 
Dmitry