On Wednesday 08 January 2014, al.stone at linaro.org wrote:

Even though support for X86 in hardware reduced mode is possible, it
is NOT enabled.  Extensive effort has gone into the Linux kernel so that
there is a single kernel image than can run on all x86 hardware; the kernel
changes run-time behavior to adapt to the hardware being used.  This is not
currently possible with the existing ACPICA infrastructure but only presents
a problem on achitectures supporting both hardware-reduced and legacy modes
of ACPI -- i.e., on x86 only.

Not sure about the logic here: While it's certainly possible to build a kernel
that runs on all x86 machines, it's also possible to build one that only
runs on some of them when some basic options are turned off. I don't see
any difference between that and what we have on ARM64 or the multiplatform
subset of ARM32.

I don't think you need any strict architecture dependency here. If you want
to make it harder for users to accidentally turn it on, I'd suggest using

config ACPI_REDUCED_HARDWARE_ONLY
       bool "Hardware-reduced ACPI support only"
       depends on !X86 || EXPERT

	Arnd