Re: [PATCH] ACPI: PCI: take native PME control on Apple machines

[Matthew Garrett]

On Thu, Oct 08, 2026 at 06:29:12PM -0500, Bjorn Helgaas wrote:
> [+cc Matthew (author of 7bc5a2bad0b8), Darrell, Andreas, Mika,
> Yehezkel, Lukas, linux-usb]
> 
> On Thu, Sep 24, 2026 at 10:28:59AM -0300, Francisco Beltrán Millalén wrote:
> > Since commit 7bc5a2bad0b8 ("ACPI: Support _OSI("Darwin") correctly")
> > negotiate_os_control() skips the _OSC handshake on Apple machines and
> > hardcodes the set of features the OS takes over, because those firmwares
> > return failure once _OSI("Darwin") has been acknowledged.  The hardcoded
> > set is ~OSC_PCI_EXPRESS_PME_CONTROL, i.e. everything except PME.  No
> > reason was given for leaving PME out.
> 
> It's clear there *was* a reason, but I don't know either.  Maybe
> Matthew will remember?

I /think/ this was the set of parameters that my machine would hand over 
via _OSC if we hadn't called _OSI("Darwin") - but it was over a decade 
ago so I can't promise that's the case. I think this probably needs to 
be tested on some older machines as well just to ensure there's no weird 
breakage as a result, but if PME is actually hooked up and there's no 
SMM managing it instead I think that's fine.