Re: Surface Pro 12in (X1P42100): touchscreen variant, different GPIOs

[François Roux]

Thank you — and I owe the list a correction, because my report was wrong at
its root.

I claimed the upstream DTS describes the touchscreen on GPIO 51/52 while my
unit uses 38/48, and concluded this was a hardware variant. It is not. There
is no variant, and there is nothing here for anyone to act on.

What I actually did wrong
=========================

x1p42100-microsoft-sp12.dts does not exist in the tree I was working from
(next-20260626). It was created *in my own tree* by a patch I had applied
myself -- Harrison's v1, which carries the GPIO 51 that he has since
described as an early mistake copied from similar devices.

So when I wrote "upstream describes 51", I was reading an obsolete patch I
had applied, and reporting it as the state of upstream. One `git log` on the
file would have shown me that. I did not run it.

Two further claims of mine were also wrong:

  - I wrote that booting the upstream DTS would leave the touchscreen dead.
    Per Harrison, GPIO 51 works but with degraded performance and missing
    pen events. Degraded, not dead.

  - I wrote that both descriptions were "internally consistent, so this is
    not a typo in either". The consistency was real but proved nothing: a
    mistake copied consistently across the interrupt property and the
    pinctrl state is still a mistake.

Where things actually stand
===========================

Harrison's v2 already fixed this, and v4

  https://lore.kernel.org/all/20260609145906.40854-2-harrison.vanderbyl@xxxxxxxxx/

is the one expected to land in 7.3. My machine's wiring (38/48) is what that
patch describes. Nothing needs discriminating, and no separate board DTS is
warranted.

Sorry for the noise. Thanks to Harrison for the quick and precise answer.

François Roux