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

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

[Daniel Palmer]

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.

The only in-kernel devicetrees that seem to use this are 4 old powerpc
ones and I couldn't work out if those boards do end up with CONFIG_ISA.

But then again it seems odd for everyone to get this code for 4 old
boards.

 drivers/of/address.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index cf4aab11e9b1..9b2f0d462fb5 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -277,6 +277,7 @@ int of_range_to_resource(struct device_node *np, int index, struct resource *res
 }
 EXPORT_SYMBOL(of_range_to_resource);
 
+#ifdef CONFIG_ISA
 /*
  * ISA bus specific translator
  */
@@ -316,6 +317,7 @@ static unsigned int of_bus_isa_get_flags(const __be32 *addr)
 		flags |= IORESOURCE_MEM;
 	return flags;
 }
+#endif
 
 static int of_bus_default_flags_match(struct device_node *np)
 {
@@ -349,6 +351,7 @@ static const struct of_bus of_busses[] = {
 		.get_flags = of_bus_pci_get_flags,
 	},
 #endif /* CONFIG_PCI */
+#ifdef CONFIG_ISA
 	/* ISA */
 	{
 		.name = "isa",
@@ -360,6 +363,7 @@ static const struct of_bus of_busses[] = {
 		.flag_cells = 1,
 		.get_flags = of_bus_isa_get_flags,
 	},
+#endif /* CONFIG_ISA */
 	/* Default with flags cell */
 	{
 		.name = "default-flags",
-- 
2.53.0

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

[Daniel Palmer]

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.

Cheers!

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

[Rob Herring]

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

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

[Daniel Palmer]

Hi Rob,

On Wed, 1 Jul 2026 at 01:48, Rob Herring <robh@kernel.org> wrote:
> > 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.

I guess I'll try sending a patch for arm64 to add CONFIG_ISA and
select it for the drivers that need the ISA bits in address.c

Thanks,

Daniel