Re: Integrating OS power management with the X server

[Nate Lawson <nate-Y6VGUYTwhu0@public.gmane.org>]

Matthew Garrett wrote:
> On Mon, 2004-10-25 at 10:26 -0700, Nate Lawson wrote:
>>This interface works for apm (except that it only has NetBSD defines 
>>currently) but is not implemented for ACPI.  I'd like more information 
>>as to what the X server actually does with this event.  Is there any 
>>situation where it actually needs to veto a suspend?  Does it 
>>potentially take seconds to save state?  Does it need to access other 
>>running subsystems or is it self-contained?
> 
> At the moment, is it still the case that X will be unhappy if there are
> any DRI clients running when going through a suspend/resume cycle?

I don't know.

> If
> so, it sounds like the server ought to reject a suspend (or,
> alternatively, use the notification to kill clients).

Or better, properly implement saving state in DRI.

> In the future, I'd expect that some dbus-related system would be
> preferable - that way X doesn't get special cased, and any application
> with good cause could reject a suspend.

The existing bsd_apm.c works for NetBSD and is the same interface as APM 
in FreeBSD.  Basically, you open /dev/apm and get notification of 
suspend requests.  Then you can continue them by sending a suspend ioctl 
or veto by just ignoring them.  The problem is, there are some times in 
ACPI when the userland cannot veto a suspend (i.e., critical battery or 
system temperature).  My plan is to initiate an unconditional suspend in 
those cases from the kernel.  Userland will have a chance to get the 
notification but if it doesn't respond within some timeout (say a few 
seconds), the kernel continues the suspend process.

The reason for my email is it's not clear what semantics X expects and 
how much it even uses this interface.

-- 
Nate


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