[PATCH xserver] present: disable page flip only when a slave crtc is active

[David Airlie]

----- Original Message -----
> From: "Michel Dänzer" <michel at daenzer.net>
> To: "Qiang Yu" <Qiang.Yu at amd.com>
> Cc: xorg-devel at lists.x.org, "David Airlie" <airlied at redhat.com>
> Sent: Tuesday, 31 January, 2017 5:04:17 PM
> Subject: Re: [PATCH xserver] present: disable page flip only when a slave crtc is active
> 
> On 26/01/17 07:13 PM, Qiang Yu wrote:
> > 
> > @@ -145,7 +157,7 @@ present_check_flip(RRCrtcPtr    crtc,
> >          return FALSE;
> >  
> >      /* Fail to flip if we have slave outputs */
> > -    if (screen->output_slaves)
> > +    if (screen->output_slaves &&
> > present_check_output_slaves_active(screen))
> >          return FALSE;
> >  
> >      /* Make sure the window hasn't been redirected with Composite */
> > 
> 
> Actually, I'm not sure why we need to check for slave outputs here at
> all. Dave, did you run into an actual problem without the check, or was
> it just a theoretical concern? The commit log says:

You don't get an output on USB without the fix.

Dave.