linux-kernel - Re: [PATCH 0/4] Driver for Apple Z2 touchscreens.

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Message-ID: <Z0Z7Lrv3rBfzac_e@google.com>
Date: Tue, 26 Nov 2024 17:51:42 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: fnkl.kernel@...il.com
Cc: Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
	Alyssa Rosenzweig <alyssa@...enzweig.io>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Henrik Rydberg <rydberg@...math.org>, asahi@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Janne Grunau <j@...nau.net>, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 0/4] Driver for Apple Z2 touchscreens.

Hi Sasha,

On Tue, Nov 26, 2024 at 09:47:58PM +0100, Sasha Finkelstein via B4 Relay wrote:
> Hi.
> 
> This series adds support for Apple touchscreens using the Z2 protocol.
> Those are used as the primary touchscreen on mobile Apple devices, and for the
> touchbar on laptops using the M-series chips. (T1/T2 laptops have a coprocessor
> in charge of speaking Z2 to the touchbar).
> 
> Originally sent as a RFC at https://lore.kernel.org/all/20230223-z2-for-ml-v1-0-028f2b85dc15@gmail.com/
> The changes since then mostly address the review feedback, but also
> add another machine that has this specific controller.
> 
> The extra gpio needed to be toggled turned out to be a quirk of the
> j293, normal CS is unusable on it, and a gpio has to be used instead.
> (j493 does not have this quirk)

I believe this needs to be done at the SPI controller level. See
"cs-gpiods" property in
Documentation/devicetree/bindings/spi/spi-controller.yaml that, as far
as I understand, allows overriding controller's native CS handling with
a GPIO when needed.

Cc-ing Mark Brown.

Thanks.

-- 
Dmitry