Re: [patch] radeonfb: FB_WAITFORVSYNC implementation

[Jon Smirl <jonsmirl@gmail.com>]

On Sat, 12 Mar 2005 14:20:24 -0500, Michel Dänzer <michel@daenzer.net> wrote:
> On Sat, 2005-03-12 at 17:12 +0000, Torgeir Veimo wrote:
> > On Sat, 2005-03-12 at 12:10 -0500, Michel Dänzer wrote:
> > > On Sat, 2005-03-12 at 17:13 +0200, Ville Syrjälä wrote:
> > > >
> > > > Also adding support for FB_ACTIVATE_VBL should be quite simple now.
> > >
> > > You don't need an interrupt for that. You can choose via the
> > > CRTC_OFFSET_CNTL:CRTC_OFFSET_FLIP_CNTL bit whether the update of the
> > > CRTC offset should take effect immediately or on the next vertical
> > > blank.
> > >
> > > Personally, I'm not sure why something that needs this functionality
> > > can't use the DRM...
> >
> > My interest for adding this is video playback. It's kind of hard to do
> > through the DRM.
> 
> You don't have to use the DRM for anything but the wait for vsync; I can
> see the effort of initializing the DRM to the point where this is
> possible being prohibitive though.
> 
> The real point is that the usage of the interrupt needs to be
> coordinated between the framebuffer device and the DRM. Something like
> the first one to request the IRQ setting up a callback mechanism where
> the other can hook into might be a possibility? Or the shared
> mini-driver that has been proposed for years, but isn't liked by some...

When we get merged my thought was to let fbdev catch the vsync IRQ and
then chain into DRM. In that model fbdev becomes the mini-driver.
Right now I don't think there is any other solution than merging
fbdev/DRM that doesn't result in some kind of dead on VT switch
scenario.

Also, I have the hotplug monitor change interrupt hookup in my local
code but I'm waiting for BenH to finish his dual head radeonfb first.
He has said it will probably be ready this week, patches are starting
to appear on lkml from him.

-- 
Jon Smirl
jonsmirl@gmail.com


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