linux-kernel - Re: [PATCH RESEND v5 0/7] Input: synaptics-rmi4 - add quirks for third party touchscreen controllers

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Message-ID: <5gcq5xsurdp24o7wndo2fm7pjsc3khco52ji34jjmeet2nidl4@rkbh4a2c4d3q>
Date: Sun, 21 Sep 2025 23:30:22 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: David Heidelberg <david@...t.cz>
Cc: Kaustabh Chakraborty <kauschluss@...root.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, "Jason A. Donenfeld" <Jason@...c4.com>, 
	Matthias Schiffer <matthias.schiffer@...tq-group.com>, Vincent Huang <vincent.huang@...synaptics.com>, 
	linux-input@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht, 
	Casey Connolly <casey.connolly@...aro.org>, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH RESEND v5 0/7] Input: synaptics-rmi4 - add quirks for
 third party touchscreen controllers

Hi David,

On Tue, Sep 16, 2025 at 11:29:45AM +0200, David Heidelberg wrote:
> On 07/08/2025 06:29, Dmitry Torokhov wrote:
> > Hi David,
> > 
> > On Thu, Jul 31, 2025 at 11:06:50PM +0200, David Heidelberg via B4 Relay wrote:
> > > With the growing popularity of running upstream Linux on mobile devices,
> > > we're beginning to run into more and more edgecases. The OnePlus 6 is a
> > > fairly well supported 2018 era smartphone, selling over a million units
> > > in it's first 22 days. With this level of popularity, it's almost
> > > inevitable that we get third party replacement displays, and as a
> > > result, replacement touchscreen controllers.
> > > 
> > > The OnePlus 6 shipped with an extremely usecase specific touchscreen
> > > driver, it implemented only the bare minimum parts of the highly generic
> > > rmi4 protocol, instead hardcoding most of the register addresses.
> > > 
> > > As a result, the third party touchscreen controllers that are often
> > > found in replacement screens, implement only the registers that the
> > > downstream driver reads from. They additionally have other restrictions
> > > such as heavy penalties on unaligned reads.
> > > 
> > > This series attempts to implement the necessary workaround to support
> > > some of these chips with the rmi4 driver. Although it's worth noting
> > > that at the time of writing there are other unofficial controllers in
> > > the wild that don't work even with these patches.
> > > 
> > > We have been shipping these patches in postmarketOS for the last several
> > > years, and they are known to not cause any regressions on the OnePlus
> > > 6/6T (with the official Synaptics controller), however I don't own any
> > > other rmi4 hardware to further validate this.
> > 
> > Sorry for not handling the patches in the last few submissions. I am
> > planning on addressing them once merge window opens.
> 
> Hello Dmitry, kind reminder about the patch series as the window is open.

I was looking at the patch series again and with the exception of patch
#5 they make little sense for sensors other than ones used in OnePlus 6.

I wonder if we could key it off of something, maybe a distinct
compatible or a property? Rob, Krzysztof, any suggestions on how to deal
with devices that do not properly implement the protocol for which they
claim compatible?

Thanks.

-- 
Dmitry