On Wed, 19 Nov 2008, Michael Schmitz wrote:
Fix panning on ARAnyM (Falcon emulation). Without this, `fbtest test011' fails
(for a 320x200x8 display with virtual 640x400).
Fails how, exactly?
It shows a corrupted display (bad line length) if xoffset & 15 != 0.
As the original code in 2.4.x was the same, I'm wondering:
o Is this a bug in the ARAnyM emulation?
o xpanstep is 1, but judging from the visual output on ARAnyM, it looks like
it should be 16?
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
drivers/video/atafb.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/video/atafb.c
+++ b/drivers/video/atafb.c
@@ -1697,8 +1697,10 @@ static int falcon_pan_display(struct fb_
}
par->hw.falcon.line_offset = bpp *
(info->var.xres_virtual - info->var.xres) / 16;
+#if 0
if (par->hw.falcon.xoffset)
par->hw.falcon.line_offset -= bpp;
+#endif;
The way I understand this code is:
If var->xoffset has the low order bits set (sub-word pixel offset)
par->hw.falcon.xoffset takes care of that, and xoffset takes care of the rest.
Since the partial word offset shifts the beginnig of the scan line into the
first word, the offset to the next scan line (par->hw.falcon.line_offset) has to
be shortened.
Sounds reasonable. But the shortening part doesn't work on ARAnyM, nor do
small panning increments. So it really smells like an ARAnyM bug.
I am pretty sure the pan step can be one (see par->hw.falcon.xoffset).
I'll test your patch as soon as I get fbtest to work (missing libgcc_s.so.2).
The alternative is to compile fbtest yourself (CVS module
FBdev/utlilities/fbtest from project linux-fbdev on sf.net).
I've been thinking of putting a git clone on kernel.org...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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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