On Thu, 14 Jan 2016 14:26:59 -0500, nick said:
>
>
> On 2016-01-14 12:32 PM, Valdis.Kletnieks@vt.edu wrote:

> >> Have you looked in -
> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/acpi/cppc_acpi.c
> >> ?
> >
> > Of course he didn't.
> >
> Or maybe he did a allmodconfig build on x86_64 bit and either that file builds correctly on x86 with

That doesn't excuse not doing a 'git grep pcc_mbox_request_channel' or a
'grep -r pcc_mbox_request_channel .', both of which would have find the caller.

> the patch applied due to it never being use on x86 or Kconfig files incorrectly set for allmodconfig
> builds on x86 for this file, or maybe my compiler is broken but I doubt that as it works for all other
> build errors similar to this.

Or you don't have the foggiest clue how Kconfig works, and don't understand
why in a 'allmodconfig' this file is *NOT* built.

Hint 1:

grep cppc drivers/acpi/Makefile
obj-$(CONFIG_ACPI_CPPC_LIB)     += cppc_acpi.o

Hint 2: In the Kconfig:

config ACPI_CPPC_LIB
        bool
        depends on ACPI_PROCESSOR
        depends on !ACPI_CPU_FREQ_PSS

config ACPI_PROCESSOR
        tristate "Processor"
        depends on X86 || IA64 || ARM64
        select ACPI_PROCESSOR_IDLE if X86 || IA64
        select ACPI_CPU_FREQ_PSS if X86 || IA64

It's left as an exercise for the reader to figure out what happens
to ACPI_CPPC_LIB when 'make allmodconfig' sets ACPI_PROCESSOR=m