On 8 January 2014 12:46, Arnd Bergmann [off-list ref] wrote:

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

quoted

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.

Would we ever need !CONFIG_ACPI_REDUCED_HARDWARE_ONLY on ARM or ARM64?
If not, we could even make this always on for these archs.

-- 
Catalin