Subject: [PATCH v5 1/5] ACPI: introduce CONFIG_ACPI_REDUCED_HARDWARE_ONLY to enforce this ACPI mode

From: [email-masked] (Arnd Bergmann)
Date: Wed, 8 Jan 2014 13:46:25 +0100

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