Re: [RFC][PATCH 0/3] PCI PM: Rework pci_set_power_state

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> I've recently discovered that pci_set_power_state() calls the platform
> callback intended for changing the state of the device after it has done
> that using the native PCI mechanism.  In my opinion this is not correct,
> because, for example, if the device is being put into D0 from a low power
> state, it may require some platform-controlled power resources to be turned
> on before that (in theory).
> 
> The following series of patches changes this function so that the platform
> callback is performed first and then the native mechanism is used.
> Additionally, however, it checks if the devices is power manageable by the
> platform and only in that case the platform callback is invoked.  For this
> purpose, I needed to add an ACPI function allowing PCI to check the power
> manageability of given device.

We have 3 cases
1. device has PCI PM only
2. device has ACPI PM only
3. device has both PCI and ACPI PM

For #1 and #2, order is moot.
For #3, how can we be sure that the new order is better than the old 
order?  Is this a theoretical patch, or is there a failure case?

thanks,
-Len


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