[PATCH] xf86-video-ati: vblank wait on crtc > 1

Michel Dänzer michel at daenzer.net
Tue Mar 22 07:23:53 PDT 2011

On Die, 2011-03-22 at 09:03 -0500, Ilija Hadzic wrote: 
> On Tue, 22 Mar 2011, Michel [ISO-8859-1] Dnzer wrote:
> > I'm still against this. At this point we know with certainty that
> > DRM_VBLANK_SECONDARY won't do what we want. In particular, if CRTC 1 is
> > disabled, the ioctl will time out, which I thought was a significant
> > part of your motivation for these changes.
> >
> > You seemed to agree with this in
> > Pine.GSO.4.62.1103041912320.20023 at umail .
> Not quite. What I said is that I want to achieve is the following 
> behavior:
> a) legacy anything (kernel or DDX), unchanged behavior from what we are
> seeing now
> b) new everything (kernel and DDX), vblanks use the right CRTC.

In the post I referenced above, you said:

> [...] I'll add a hook to the DDX to check the version and not issue
> the ioctl at all if it is requested on a higher CRTC. I think that's
> better than falling back to the old style and issuing the system call
> on (potentially wrong) CRTC #1 because that can block the application
> (and I'd rather see it proceed without attempting vblank
> synchronization, then block).

Which made sense then and still does now, in contrast to trying to
preserve ill-defined broken behaviour.

> >> +	} else {
> >> +	    if (cap_value) {
> >> +		info->high_crtc_works = TRUE;
> >> +	    } else {
> >> +		xf86DrvMsg(pScrn->scrnIndex, X_WARNING, "Your kernel does not handle VBLANKs on CRTC>1\n");
> >> +		info->high_crtc_works = FALSE;
> >
> > Is there any point in having two different warning messages? I think
> > 'CRTC > 1' could use spaces.
> There is a point: one warning tells you that the kernel is old and you 
> have to upgrade. The other warning tells you that the kernel is new enough 
> (it has the GET_CAP ioctl), but for some other reason refused to handle 
> high-crtcs (which at this time doesn't exist, but it should not be the 
> reason to "destroy" the information).

Fair enough.

> I bet the change on my desk in my office that if I had the blankspace, 
> someone would have responded with an opposite suggestion ;-).

That's bold of you. I stand by my request.

Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer

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