Re: Re: [PATCH]: image.depth fix to accomodate monochrome cards

On 9 Jan 2003, Antonino Daplas wrote:

On Wed, 2003-01-08 at 17:52, Geert Uytterhoeven wrote:

quoted

On 8 Jan 2003, Antonino Daplas wrote:

quoted

On Wed, 2003-01-08 at 05:06, Geert Uytterhoeven wrote: 

quoted

On 8 Jan 2003, Antonino Daplas wrote:

quoted

2.  diff submitted by Geert: cleaner logo data preparation for
monochrome cards and correct initialization of palette_cmap.transp.

I'll have to do some more fixes there, since the monochrome logo is used not
only on monochrome displays, but on all other displays with bits_per_pixel < 4
Since the pixel data in fb_image are colormap indices, they have to reflect the
correct `black' and `white' colors on such displays.

E.g. on amifb (which supports all bits_per_pixel from 1 through 8) the logo
showed up in black-and-blue with bits_per_pixel == 3, cfr. the first two
entries of {red,green,blue}8[] in fbcmap.c.

Hmm, I see.  I think only linux_logo_bw will be the only one affected,
since linux_logo_16 happens to match the console palette and in
linux_logo, we either reset the palette and/or the cmap.

Indeed.

quoted

Would expanding each bit to the full bit depth work?  Ie for bpp=8 using
monochrome data, white is 0 and black is 0xff.

For bpp=8 that won't work, since we have 16 console colors only :-)

Of course :-)

quoted

But for bpp=[1-3] that's OK, cfr. fbcmap.c.

BTW, perhaps it makes sense to just pass the appropriate `black' and `white'
pixel values to the logo conversion routine? Preferably through a 2-element
array, so we can index it with the logo data bit value instead of using
tests/branches. Then we'd have:

Something like this?

static void fb_set_logo(struct fb_info *info, u8 *logo, int needs_logo)
{
	int i, j;
	u8 mask[2] = {0,0};

	switch (needs_logo) {
	case 4:
		for (i = 0; i < (LOGO_W * LOGO_H)/2; i++) { 
			logo[i*2] = linux_logo16[i] >> 4;
			logo[(i*2)+1] = linux_logo16[i] & 0xf;
		}
		break;
	case 1:
	case ~1:
		mask[1] = (u8) ~(BIT_SHIFT(0xffff, info->var.bits_per_pixel));
		for (i = 0; i < (LOGO_W * LOGO_H)/8; i++) {
		       u8 d = linux_logo_bw[i];
                       for (j = 0; j < 8; j++, d <<= 1)
                               logo[i*8+j] = mask[((d ^ needs_logo) >> 7) & 1];
		}
		break;
	}
}

Yes, looks ok.

BTW, you can get rid of the `d ^ needs_logo' inside the loop by initializing
mask[] based on the value of needs_logo.

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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