Re: [Linux-fbdev-devel] 2 pm3fb questions/problesm ...

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

On Tue, 19 Jun 2001, Sven LUTHER wrote:
> On Tue, Jun 19, 2001 at 03:55:28PM +0200, Geert Uytterhoeven wrote:
> > On Tue, 19 Jun 2001, Sven LUTHER wrote:
> > > On Tue, Jun 19, 2001 at 02:08:11PM +0000, Petr Vandrovec wrote:
> > > > for truecolor and 4bpp pseudocolor, 0x0f0f0f0f is correct for
> > > > 8bpp pseudocolor, 0xXX0f0f0f (*) is for 24/32bpp directcolor,
> > > > 0x3DEF3DEF for 15bpp, 0x79EF79EF for 16bpp, and you cannot
> > > > use RGB332 truecolor without information loss.
> > > 
> > > mmm, truecolor is when the the rgb value is written directly to the pixel ?
> > > and pseudo color is when you use a color index table.
> > > 
> > > What exactly is direct color ?
> > 
> > truecolor:
> > 
> >     red = (pixel & redmask) >> redshift
> >     green = (pixel & greenmask) >> greenshift
> >     blue = (pixel & bluemask) >> blueshift
> > 
> > pseudocolor:
> > 
> >     red = redtable[pixel]
> >     green = greentable[pixel]
> >     blue = bluetable[pixel]
> > 
> > directcolor:
> > 
> >     red = redtable[(pixel & redmask) >> redshift]
> >     green = greentable[(pixel & greenmask) >> greenshift]
> >     blue = bluetable[(pixel & bluemask) >> blueshift]
> > 
> > To make sure revc always does the correct thing, there should be a 17th entry
> > in the display->dispsw_data telling the invertion mask.
> 
> And the correct thing to do is ?

EXOR with 15 for pseudocolor
EXOR with -1 for truecolor
EXOR with (15 << redshift | 15 << greenshift | 15 << blueshift) for directcolor

The directcolor case assumes your driver loaded the console palette to the DAC.
Some fbdevs load a linear palette to the DAC so it behaves like truecolor. In
that case, EXOR with -1. That's the reason why we need the 17th entry: fbcon-*
cannot guess easily which mode is being used.

Gr{oetje,eeting}s,

						Geert

--
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