http://bugzilla.kernel.org/show_bug.cgi?id=12748
--- Comment #27 from ykzhao <yakui.z...@intel.com> 2009-07-06 02:33:12 ---
(In reply to comment #26)
> (In reply to comment #25)
> > (In reply to comment #24)
> > > Due to the D3 problem of some devices, PCI will *NOT* place any devices
> > > in D3
> > > right now (which is bad). I hope they will fix it soon, so that only
> > > broken or
> > > problematic devices will not be put in D3.
> > If the PCI device can't be put in PCI_D3HOT/PCI_D3cold when unloading device
> > driver, how can we put the corresponding ACPI device into D3 state?
> > Maybe when we put the corresponding ACPI device into D3 state, the power
> > resource is turned off, which causes that the PCI device can't work well.
>
> Indeed, we will (unfortunately) have devices that are _never_ put in ACPI D3,
> but the module (driver) for these devices _will_ be removed (rmmod).
>
> So, as far as I can see, ACPI power resource handling MUST:
>
> 1. release the power resource from the device before the device is removed,
> even if it is not put it in D3 (you can set a marker to never turn off the
> power resource for devices that are removed without being put in D3).
The main purpose of releasing the reference between power resource and device
is to turn off the power resource when it is not used by any device.
what is the meaning of setting the marker to never turn off the power resource?
>
> OR
>
> 2. stop using pointers to devices in the power resources, so that it doesn't
> crash the kernel after a rmmod...
This is not an issue. The acpi device is not removed after a rmmod. So it won't
crash the kernel even when we access the corresponding ACPI device. At the same
time the power resource is used internally by the ACPI device. It is not
meaningful to get by which device it is used. Instead at most case we will get
the power resources for one ACPI device.
In fact IMO the purpose of this bug is to disable the power resource when it is
not used by any device. This includes the following two cases:
a. the power resource is never used by any device.
b. the Device power state is in D3. We had better disable the power
resource used by it. If the device power state is in D0, we can't turn off the
power resource even when there is no device driver for the corresponding PCI
device.
>
> I think (1) is best. Do you have any other ideas for solving this problem?
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