linux-kernel - Re: [RFC PATCH 1/2] of: Add a variant of of_device_is_compatible() that can be build time culled

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Message-ID: <20260109142907.GA3059757-robh@kernel.org>
Date: Fri, 9 Jan 2026 08:29:07 -0600
From: Rob Herring <robh@...nel.org>
To: Daniel Palmer <daniel@...ngy.jp>
Cc: linusw@...nel.org, brgl@...nel.org, saravanak@...nel.org,
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] of: Add a variant of of_device_is_compatible()
 that can be build time culled

On Fri, Jan 09, 2026 at 11:51:52AM +0900, Daniel Palmer wrote:
> Hi Rob,
> 
> On Fri, 9 Jan 2026 at 08:38, Rob Herring <robh@...nel.org> wrote:
> >
> > On Wed, Jan 07, 2026 at 12:07:30PM +0900, Daniel Palmer wrote:
> > > In a lot of places we are using of_device_is_compatible() to check for quirks
> >
> > I'm assuming 'a lot' is not just 3 places? Got a rough estimate?
> >
> > This seems fine to me assuming there are more.
> 
> In core code (like the gpio core, and not in a specific driver) there
> are only a few places. I think around 10.
> There are more when we get into drivers that handle lots of variants
> of the same hardware and check the compatible string during probe.
> (There are ~700 calls to of_device_is_compatible() in drivers/, most
> of which seems to be quirks checking during probe).

Generally in drivers, it is preferred to use match data rather than 
of_device_is_compatible(). And if we're going in and touching 
of_device_is_compatible() in drivers, that's what we want to do. Using 
match data of course doesn't help your cause of reducing size. I suppose 
you could define a macro that includes a compatible in the match table 
or not. If the match data is function ptrs, then if those functions 
aren't referenced, they would be dropped by the compiler.

Rob