RE: [Linux-fbdev-devel] API prototype doc

[Geert U. <ge...@li...>]

On Mon, 3 Dec 2001, Sottek, Matthew J wrote:
> >oo, are there cases where extra pitch memory is used for things?  the area
> is 
> >so broken up and in small chunks that i didnt think any hardware developer 
> >would use it.  but if intel's do that, i'd imagine there is probably
> something 
> >there.  this certainly causes problems i wasn't aware of.
>  
> Well I don't use the extra, but I could :) I was looking for a cheap example
> of when you wouldn't want mmap to happen. Some hardware have tiled memory
> framebuffers that might not work correctly unless you knew about the
> tiling. Intel's tiled memory isn't a problem, but I think some might be.
> 
> The extra pitch-width area isn't useless. You can put other surfaces there.
> You think of the area as being broken up, but really it is just a thinner
> area with the same pitch as the framebuffer. i.e. if your framebuffer is
> 800x600 at 16bit, on Intel hardware you have a fb pitch of 2048. That
> is an area of 448x600 with a pitch of 2048 that can be used.

There exist PowerMac graphics cards that put the hardware cursor in that area.

Gr{oetje,eeting}s,

						Geert

P.S. Matt: I'm still reading your document (I'm halfway). I'll post my list of
     questions and comments after I've finished reading the whole document. So
     far it looks nice!
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@li...

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds