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.