Re: [PATCH 1/3] PCI: Add helper to check if any of ancestor device support D3cold

[Mika Westerberg]

Hi,

On Thu, Aug 24, 2023 at 12:46:43PM +0800, Kai-Heng Feng wrote:
> In addition to nearest upstream bridge, driver may want to know if the
> entire hierarchy can be powered off to perform different action.
> 
> So walk higher up the hierarchy to find out if any device has valid
> _PR3.

I'm not entirely sure this is good idea. The drivers should expect that
the power will be turned off pretty soon after device enters D3hot. Also
_PR3 is not PCI concept it's ACPI concept so API like this would only
work on systems with ACPI.