Re: [RFC] Reliable video POSTing on resume (was: Re: [ACPI] SamsungP35, S3, black screen (radeon))

[Bill Davidsen]

Alan Cox wrote:
> On Sad, 2005-02-05 at 09:35, Pavel Machek wrote:
>
> > Rumors say that notebooks no longer have video bios at C000h:0; rumors
> > say that video BIOS on notebooks is simply integrated into main system
> > BIOS. I personaly do not know if rumors are true, but PCs are ugly
> > machines....
> > 							
>
>
> A small number of laptop systems are known to pull this trick. There are
> other problems too - the video bios boot may make other assumptions
> about access to PCI space, configuration, interrupts, timers etc.
>
> Some systems (intel notably) appear to expect you to use the bios
> save/restore video state not re-POST.

Isn't that what it's there for? In any context other than save/restore I 
wouldn't think using the BIOS was a good approach. But this is a special 
case, and if there's a BIOS function which does the right thing, it 
would seem to be easier to assume that the BIOS works than that the 
driver can do every operation for a clean restart.

The problem is that while POST leaves the video in a known state, it may 
not the known state you want, nor is it a given that you can get from 
there to where you were on suspend. PC hardware isn't always that 
dependable.

--
bill davidsen <davidsen@xxxxxxx>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979
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