Re: [PATCH] fbdev: atafb: Restrict SuperBlitter to supported formats

Hi Geert,

Am 08.09.2026 um 19:18 schrieb Geert Uytterhoeven:

quoted

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Unless I overlooked something, the fill also looks wrong on paper: the
first line is filled with a repeated byte and then with repeated
32-bit words of the same value, which cannot reproduce a 3-byte pixel
pattern unless all three bytes are equal.

You're correct - we'd need a memset24() to account for that. Without

Unless the frame buffer would be using a DIRECT_COLOR visual (which
is not the case), then you could draw pixels in the 16 console colors
by replicating the color index in all 3 bytes ;-)

Sorry, I don't get that - are the console colors chosen judiciously to 
allow for that?

quoted

hardware support this is an academic exercise that I don't have time for :-)

True. And as this code is used only to fill the first line (the blitter
replicates it into the other lines), the performance difference between
a simple byte loop and a true memset24() won't be that large.

I wasn't worried about performance as the blitter takes care of most of 
the work (though we may schedule away from svblit_fillrect() while the 
blitter is active). Getting the 'simple byte loop' right is more 
important. My sample code got everything wrong in fact.

There's a reason why we don't work with 24 bit sized objects usually, 
and probably a reason why 24 bpp was never implemented for the 
SuperVidel :-)

Cheers,

	Michael

Gr{oetje,eeting}s,

                        Geert