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

[Rob Herring <robh@kernel.org>]

On Sun, Sep 21, 2025 at 11:30:22PM -0700, Dmitry Torokhov wrote:
> 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?

A compatible is "the way" as David has done. Once again, generic 
compatibles have proven inadequate.

Rob