Build error in 6.16-rc1 in drivers/mfd/88pm860x-core.c

Peter Schneider
2025-06-09T01:58:45Z

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Hi all,

I just tried to test-build 6.16-rc1 on my good old 2-socket Ivy Bridge Xeon E5-2697 v2
server, running Proxmox/Debian 12 (Bookworm) with GCC 12.2. I received the following build
error:

CC drivers/mfd/88pm860x-core.o
drivers/mfd/88pm860x-core.c: In function 'device_irq_init':
drivers/mfd/88pm860x-core.c:576:29: error: unused variable 'node' [-Werror=unused-variable]
576 | struct device_node *node = i2c->dev.of_node;
| ^~~~
cc1: all warnings being treated as errors
make[4]: *** [scripts/Makefile.build:287: drivers/mfd/88pm860x-core.o] Error 1
make[3]: *** [scripts/Makefile.build:554: drivers/mfd] Error 2
make[2]: *** [scripts/Makefile.build:554: drivers] Error 2
make[1]: *** [/usr/src/linux/Makefile:2006: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2

My config file is attached. I always build with CONFIG_WERROR=y (same as I do in all of my
regular test builds of Greg's stable-RC releases).

I'm not a Kernel developer nor a C programmer, I only have superficial knowledge of C (but
I love to test and to tinker), so I don't quite understand this warning/error message.
Becauses some lines below, the node variable is used as a paramter to the of_fwnode_handle
macro (from include/linux/of.h):

irq_domain_create_legacy(of_fwnode_handle(node), nr_irqs, chip->irq_base, 0,
&pm860x_irq_domain_ops, chip);

Does that not count as variable usage to the compiler? Digging in somewhat deeper, I found
that probably the patch from [1] is missing in 6.16 and should have been included?!

When I apply that patch, my build succeeds.

[1]: https://lore.kernel.org/all/20250602201008.1850418-1-superm1@kernel.org/

Beste Grüße,
Peter Schneider

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