writing a framebuffer driver and font problem..

writing a framebuffer driver and font problem..

[Kaj-Michael Lang]

Hello..

I hope someone here can help me. I've started writing support for the b/w
framebuffer on
VAXstation for the Linux/VAX project. And I've got so far that it sort-of
works, I can output text
on the framebuffer and such. Problem is that all font are flipped/mirrored,
like a "b" looks like "d", this picture
might show it a little bit better: http://home.tal.org/~milang/vax/2.html
And as you can se from the picture the logo looks strange.

What might be the problem, and what should I do to fix it ?

I'm totaly new a writing kernel code so it might be something obvious that
I'm missing.

-- 
Kaj-Michael Lang , milang@tal.org



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Re: writing a framebuffer driver and font problem..

[Geert Uytterhoeven]

On Fri, 31 Oct 2003, Kaj-Michael Lang wrote:
> I hope someone here can help me. I've started writing support for the b/w
> framebuffer on
> VAXstation for the Linux/VAX project. And I've got so far that it sort-of
> works, I can output text
> on the framebuffer and such. Problem is that all font are flipped/mirrored,
> like a "b" looks like "d", this picture
> might show it a little bit better: http://home.tal.org/~milang/vax/2.html
> And as you can se from the picture the logo looks strange.
> 
> What might be the problem, and what should I do to fix it ?
> 
> I'm totaly new a writing kernel code so it might be something obvious that
> I'm missing.

Are you using 2.4 or 2.6?

You have to swap the character data in
drivers/video/fbcon-mfb.c:fbcon_mfb_putc{,s}() (2.4.x) or
drivers/video/cfbimgblt.c.

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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Re: writing a framebuffer driver and font problem..

[Kaj-Michael Lang]

On Fri, 2003-10-31 at 12:41, Geert Uytterhoeven wrote:
> Are you using 2.4 or 2.6?

2.4 for now, but I'm going to port it over to 2.6.

> You have to swap the character data in
> drivers/video/fbcon-mfb.c:fbcon_mfb_putc{,s}() (2.4.x) or
> drivers/video/cfbimgblt.c.

Ok.. stupid question.. how do I do that ?

-- 
Kaj-Michael Lang <milang@tal.org>



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Re: writing a framebuffer driver and font problem..

[Geert Uytterhoeven]

On Fri, 31 Oct 2003, Kaj-Michael Lang wrote:
> On Fri, 2003-10-31 at 12:41, Geert Uytterhoeven wrote:
> > Are you using 2.4 or 2.6?
> 
> 2.4 for now, but I'm going to port it over to 2.6.
> 
> > You have to swap the character data in
> > drivers/video/fbcon-mfb.c:fbcon_mfb_putc{,s}() (2.4.x) or
> > drivers/video/cfbimgblt.c.
> 
> Ok.. stupid question.. how do I do that ?

This (untested) patch should do the trick...

--- linux-2.4.x/drivers/video/fbcon-mfb.c.orig	2001-10-02 11:47:46.000000000 +0200
+++ linux-2.4.x/drivers/video/fbcon-mfb.c	2003-10-31 13:14:47.000000000 +0100
@@ -19,6 +19,15 @@
 #include <video/fbcon-mfb.h>
 
 
+static inline u8 swap_byte(u8 in)
+{
+    in = ((in & 0xf0) >> 4) | ((in & 0x0f) << 4);
+    in = ((in & 0xcc) >> 2) | ((in & 0x33) << 2);
+    in = ((in & 0xaa) >> 1) | ((in & 0x55) << 1);
+    return in;
+}
+
+
     /*
      *  Monochrome
      */
@@ -97,7 +106,7 @@
     underl = attr_underline(p,c);
 
     for (rows = fontheight(p); rows--; dest += p->next_line) {
-	d = *cdat++;
+	d = swap_byte(*cdat++);
 	if (underl && !rows)
 	    d = 0xff;
 	else if (bold)
@@ -127,7 +136,7 @@
 	dest = dest0++;
 	cdat = p->fontdata+c*fontheight(p);
 	for (rows = fontheight(p); rows--; dest += p->next_line) {
-	    d = *cdat++;
+	    d = swap_byte(*cdat++);
 	    if (underl && !rows)
 		d = 0xff;
 	    else if (bold)

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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