linux-kernel - Re: [PATCH] [RFC] of: Add debug aid to find unused device tree properties

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Message-ID: <3247761.5fSG56mABF@somecomputer>
Date: Mon, 14 Oct 2024 10:51:51 +0200
From: Richard Weinberger <richard@...ma-star.at>
To: Richard Weinberger <richard@....at>, devicetree@...r.kernel.org
Cc: robh@...nel.org, saravanak@...gle.com, linux-kernel@...r.kernel.org, upstream+devicetree@...ma-star.at, Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH] [RFC] of: Add debug aid to find unused device tree properties

Krzysztof,

Am Montag, 14. Oktober 2024, 09:49:14 CEST schrieb 'Krzysztof Kozlowski' via upstream:
> On Sun, Oct 13, 2024 at 10:07:30PM +0200, Richard Weinberger wrote:
> > This is a proof-of-concept patch that introduces a debug feature I find
> > particularly useful.  I frequently encounter situations where I'm
> > uncertain if my device tree configuration is correct or being utilized
> > by the kernel.  This is especially common when porting device trees
> > from vendor kernels, as some properties may have slightly different
> > names in the upstream kernel, or upstream drivers may not use certain
> > properties at all.
> 
> In general I don't mind, but I have a comment about above rationale.
> It's just wrong. The point of DT is to describe hardware, not the one
> given, fixed in time implementation.

I agree with you, sorry for being imprecise.

> What's more, writing bindings mentions this explicit: make binding
> complete, even if it is not used.

Yes, with this aid, it is IMHO easier to find bindings that need attention.
Just as an example, lately the device tree of a vendor used the property "timers",
but in mainline it is "ti,timers".  With this debug feature, it is easy to see that
"timers" is not being used, and somebody has to decide whether the property is
really not used by a driver, or if the binding needs more work.

Thanks,
//richard


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