Re: [PATCH] of/address: Drop ISA parts when !CONFIG_ISA

[Rob Herring <robh@kernel.org>]

On Sun, Jun 28, 2026 at 02:44:51PM +0900, Daniel Palmer wrote:
> Hi Daniel, (Replying to myself..)
> 
> On Sat, 27 Jun 2026 at 02:19, Daniel Palmer <daniel@thingy.jp> wrote:
> >
> > The PCI parts are already wrapped in #ifdef CONFIG_PCI
> > so it seems sensible to add #ifdef CONFIG_ISA around the ISA
> > parts.
> >
> > This reduces the code/data size a bit on configs with !CONFIG_ISA.
> >
> > Signed-off-by: Daniel Palmer <daniel@thingy.jp>
> > ---
> >
> > Sorry for the spam, somehow I botched sending a patch..
> >
> > I thought about making this RFC as I'm a bit unsure if machines
> > that need this ISA stuff actually select CONFIG_ISA or not.
> 
> So sashiko worked out what is going on here. A few machines have
> things connected via an LPC bus that is derived from ISA and needs the
> code to parse those nodes but those machines don't select CONFIG_ISA.
> There seem to be ~15 devicetrees in total that actually need it (1 in
> x86, 1 in arm64, a few in mips/loongson for loongson machines, and
> then a few in ppc).
> 
> I made a series that adds CONFIG_OF_ISA to enable this code, selects
> it in the places that needs it, and then does the original part of
> disabling the code if not needed. I will wait a bit before sending.
> The reason to do this is I am using devicetree to boot a machine with
> 4MB of RAM and a 7MHz CPU. Removing dead code/data like this helps.

I tend to not want more CONFIG_OF_foo options, but okay I guess.

Alternatively, maybe CONFIG_ISA should just be enabled with these 
drivers. Doesn't really look like there's actually much or any code for 
CONFIG_ISA. The biggest issue might be the option doesn't exist on 
arm64.

Rob