Re: Re: HP300 support checked in

On Wed, 14 Jul 2004, Antonino A. Daplas wrote:

On Monday 12 July 2004 15:25, Geert Uytterhoeven wrote:

quoted

On Sun, 11 Jul 2004, Kars de Jong wrote:

quoted

Support for <8 bit framebuffers is probably broken. I don't know how I'm
going to support them yet. It used to be "special-cased" in
drivers/video/fbcon.c.

They are laid out in memory like normal 8 bit chunky framebuffers, but
the upper bits are basically ignored.

So for blitting purposes the bits_per_pixel == 8 code should be used,
but just setting bits_per_pixel to 8 doesn't work because then the
amount of colours is assumed to be 256.

I think we basically need to distinguish between bpp and depth.

quoted

What are the possible values of depth? Just 1 (monochrome)? Or also 4 (16
colors)?

If it's just 1 (monochrome), you can probably get away with setting
var.bits_per_pixel = 256 and fix.visual = FB_VISUAL_MONO01 (or MONO10).

Or we can use the fields in var->green, var->red, var->blue, ie,  to describe a 4-color
8-bit chunky framebuffer:

var->red.length = 2;
var->red.offset = 0;
var->green = var->blue = var->red.
var->bits_per_pixel = 8;

This breaks something different, since for pseudocolor visuals, the *.lengths
indicate the sizes of the CLUT entries (e.g. 8 bit per component for modern
24-bit color, 6 bit for VGA-style 18-bit color).

We still need to fix fbcon to handle this type of framebuffers, since fbcon always assumes
a packed pixel format.  For instance, we have this kind of code in fbcon.c

vc->vc_can_do_color = (var->bits_per_pixel != 1) ? 1 : 0;

which is incorrect in this case. Better if we test fix->visual instead.

Yep, that one should test the visual. And in this case greyscale count as color
as well...

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


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