apm_emulation regression

[Johannes Berg]

On Wed, 2007-12-12 at 13:45 +1100, Benjamin Herrenschmidt wrote:
> I only just noticed a huge regression that was introduced when we moved
> PowerPC to the generic APM emulation code instead of our own. I'm in
> large part to blame since I acked the patch...
> 
> Basically, what we lost is the mechanism for notifying user applications
> and waiting for their ACK before proceeding to system suspend. The new
> generic code will still do that ... only when the actual suspend request
> initiates from an APM suspend ioctl.

Indeed.

> For any other suspend (via our private PMU ioctl or via the sysfs
> interface), userspace will -not- be notified.

Right.

> That basically means X will break. That's why X broke on the latest
> ubuntu until I whacked some new scripts in them to force console
> switching, among other things. Possibly other apps that relied
> on /dev/apm_bios to be notified of system suspend/resume broke as well.

Ah. I guess I never noticed because I had the scripts to do console
switching all along.

> Now the question is that is it still work trying to fix it ? That would
> probably require APM emulation hooking at a fairly high level into the
> generic PM code to trigger the signaling & waiting of processes before
> freeze & device suspend among others...

Yeah, bit icky... but doable. Rafael, any ideas?

johannes
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