Re: fixing fbdev for various framebuffer configs

[Jon Smirl <jonsmirl@gmail.com>]

On 7/29/05, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Fri, 29 Jul 2005, Jon Smirl wrote:
> > It has been determined that bits per pixel is insuffucient to
> > enumerate all the needed fbconfigs. Here are the possible fgconfigs
> > from the OpenGL headers:
> >
> > total bits
> > 8     GL_R3_G3_B2
> > 8     GL_RGBA2
> > 12   GL_RGB4
> > 15   GL_RGB5
> > 16   GL_R5_G6_B5
> > 16   GL_RGBA4
> > 16   GL_RGB5_A1
> > 24   GL_RGB8
> > 30   GL_RGB10
> > 32   GL_RGBA8
> > 32   GL_RGB10_A2
> > 36   GL_RGB12
> > 48   GL_RGB16
> > 48   GL_RGBA12
> > 64   GL_RGBA16
> 
> All above (and many more) can be handled fine, cfr.
> fb_var_screeninfo.{red,green,blue,transp}.
> 
> > 48   GL_FLOAT_RGB16
> > 64   GL_FLOAT_RGBA16
> > 96   GL_FLOAT_RGB32
> > 128 GL_FLOAT_RGBA32
> >
> > We need to be able to set any of these through the fbdev interface. We
> > also need to allow for possible future expansion.
> >
> > Ideas on how to adjust the fbdev interface?
> 
> Floating point pixel values could be handled by a new nonstd flag:

Why non-standard? All of the current higher end ATI/Nvidia cards support it.

> 
>     #define FB_NONSTD_FLOAT     2
>     fb_var_screeninfo.nonstd |= FB_NONSTD_FLOAT
> 
> > What is the effect of alpha bits on the scanout buffer, do they do anything?
> 
> They determine the transparency of the pixel w.r.t. to the underlying plane, if
> the hardware supports it.
> 
> Gr{oetje,eeting}s,
> 
>                                                 Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> 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
> 


-- 
Jon Smirl
jonsmirl@gmail.com


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