Re: [patch] radeonfb: FB_WAITFORVSYNC implementation

["Ville Syrjälä" <syrjala@sci.fi>]

On Sat, Mar 12, 2005 at 12:10:22PM -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.

Great. Matrox and mach64 chips don't have such a bit so they need 
to perform the flip/pan from the interrupt handler.

> Personally, I'm not sure why something that needs this functionality
> can't use the DRM...

I think the DRM is a real bitch to use. It requires a lot of hw specific 
init code and AFAIK it needs root privilidges to get to the state where 
you can actually use it. It's much easier to use fbdev. And IMO logically 
that's where the vblank interrupt belongs since fbdev is the one 
programming the CRTC.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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