Re: [linux-fbdev] New api again

[Petr V. <VAN...@vc...>]

On 17 Jan 01 at 12:11, James Simmons wrote:
> Okay. This answered my previous question. It pretty much comes down to
> choosing between xxxfb_setcolreg or xxxfb_set_cmap. Their are pros and
> cons to having each:
>                   
> xxxfb_setcolreg  
> PRO:         can change a individual register without having to monkey
>              with the entire CLUT. 
> 
> CONS:        Hardware designs. Some hardware require vsync when changing
>          the color palette.
> 
> xxxfb_set_cmap
> PRO:         More flexiable with bizarre hardware. Also works nice with 
>          hardware that has more than one CLUT. In this case we can
>          cache a bunch of color maps and switch the index around.      
>                      
> CONS:        Can't change a subset of teh CLUT table easily. 

Adding 'CMAP_FIRST' and 'CMAP_MORE' bits as additional setcolreg
argument? And set CMAP_FIRST for first entry of cmap, and CMAP_MORE
if it is not last entry? So VGA could do:

  if (flags & CMAP_FIRST) {
    outb(reg, 0x3C8);
  }
  outb(red, 0x3C9);
  outb(green, 0x3C9);
  outb(blue, 0x3C9);
  
I have no idea whether someone really needs CMAP_MORE. Maybe if you
must enable legacy VGA I/O region for doing palette changes... Or if
you must switch DAC back to 6bit mode for legacy apps.
                                            Best regards,
                                                Petr Vandrovec
                                                van...@vc...