On 11/25/2013 10:45 AM, Matthew Garrett wrote:
On Mon, Nov 25, 2013 at 10:43:27AM -0700, Al Stone wrote:
On 11/25/2013 08:30 AM, Matthew Garrett wrote:
Is ACPI_REDUCED_HARDWARE supposed to indicate support for the reduced
hardware profile, or that the platform *only* implements the reduced
hardware profile?
From what I can see in ACPICA, ACPI_REDUCED_HARDWARE indicates the
platform *only* implements the reduced hardware profile. This *seems*
to be consistent with the specification -- see 3.11.1, second bullet,
for example:
Ok, so a kernel built without ACPI_REDUCED_HARDWARE would still support
the reduced hardware profile?
Let me check on that. The reduced hardware profile is a pretty
strict subset, and I think I can see a way where I could force
selecting the reduced HW profile on boot if the kernel has been
built *without* ACPI_REDUCED_HARDWARE. What I am not convinced
of is that all of the proper guards are in place in ACPICA -- I
trust that they have been, but I would like to double check.
If I can get that to work properly, I'll add it to this patch set.
...if by "not supported" one takes that to mean "does not exist when
compiled." I can look at the ACPICA code again, just the same; perhaps
there is some reasonable way to at least select one or the other at boot
as the first step, and then allow switching between modes as a later
step.
I don't think you'd ever want to switch after init time. There's a flag
in the FADT that indicates whether a system is implementing the reduced
hardware profile or not.
Agreed. I could see it as something to use when experimenting perhaps,
but I think just allowing the switch at boot would cover the majority
of the use cases.
--
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Linaro Enterprise Group
al.stone@xxxxxxxxxx
-----------------------------------
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