linux-kernel - Re: [PATCH] dt-bindings: firmware: coreboot: Document optional device specific properties

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Message-ID: <CAGXv+5HePVim+-fx0bG-geBHp3kLQbNGLyknGRx=LgLZ7H+DUQ@mail.gmail.com>
Date: Wed, 19 Nov 2025 16:54:28 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org, 
	chrome-platform@...ts.linux.dev, Julius Werner <jwerner@...omium.org>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: firmware: coreboot: Document optional device
 specific properties

On Wed, Nov 19, 2025 at 4:13 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 19/11/2025 08:32, Chen-Yu Tsai wrote:
> > On Wed, Nov 19, 2025 at 3:13 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> >>
> >> On 19/11/2025 08:11, Chen-Yu Tsai wrote:
> >>> Coreboot, or the ChromeOS second stage bootloader, depthcharge, will
> >>> insert device specific properties into the coreboot firmware node when
> >>> there are valid values.
> >>>
> >>> Document these properties in the binding.
> >>>
> >>> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> >>> ---
> >>>  Documentation/devicetree/bindings/firmware/coreboot.txt | 9 +++++++++
> >>>  1 file changed, 9 insertions(+)
> >>>
> >>
> >> TXT files cannot receive new properties. You need to first convert to DT
> >> schema.
> >
> > OK. Let me look into this.
>
> After the conversion you will hit another problem - you need vendor
> prefixes for these, because only generic properties can come without
> them. Otherwise (without vendor prefix) these would define the type for
> all other bindings, which probably is not what we want.

I understand the concern. But given it's specifically under the
/firmware/coreboot node, which is inserted by coreboot, doesn't that
already serve as a namespace or vendor prefix?

FWIW the ship has already sailed for naming. The first three properties
were added to depthcharge [1] and coreboot [2] in 2018. The last property
was added to depthcharge in 2023 [3]. That is what has shipped in immutable
firmware on ARM-based Chromebooks since the RK3399 days. The coreboot
change was presumably added for other devices.

This change only serves to document what the firmware already provides.
Whether they should be grandfathered in or not doesn't change what the
firmware already does; it just makes it more well known. It's not going
to have any effect on validation either, as the properties are supposed
to be inserted by the bootloader, not added statically to dts files.

Presumably we can update the code to use a new name, but we still have
to live with the old names for up to 10 years.

ChenYu

[1] https://crrev.com/c/1028728
[2] https://review.coreboot.org/c/coreboot/+/28104
[3] https://crrev.com/c/4975217