Re: [Linux-fbdev-devel] Comments on fbgen.c and fbcon-accel.c

From: Antonino Daplas (
Date: Sat May 04 2002 - 10:48:47 EST

On Sat, 2002-05-04 at 05:47, James Simmons wrote:
> > I have a few observations on fbgen and fbcon-accel.
> Don't mix fbgen with fbcon-accel. The new gen_* stuff in fbgen.c is meant
> to replace the old fbgen_* stuff. That is why the below doesn't work.
Okay, I've succeeded in rewriting the i810/i815 driver to use the gen_*
stuff instead of fbgen_*. As far as I can tell everything works :) --
y-panning, accel, etc -- although gen_update_var() may not work
properly. I'm still getting incorrect cursor colors in 8 bpp, but
that's probably my fault. And you're right, it's actually easier to
write the driver using the gen_* stuff.

> > 2. Also, fbgen_switch basically just do an fbgen_do_set_var()
> > (decode_var(), followed by set_par()). This is okay most times, but
> > it's probably better if fbgen_switch also does an encode_fix() since
> > fbcon's drawing functions also rely on fix->line_length.
> Most likely that is also broken. I haven't thought about it since I plan
> to make all the old fbgen_* functions go away.
fb_gen_switch may be broken, but I think gen_switch works just okay as
long as info->fix is updated in set_par().

> > If an fb_fix_screeninfo is not updated, display corruption occurs when
> > switching to another display with a different pixelformat.
> Correct. That is why I require info->fix to be updated when set_par is
> called.

The i810fb patch is at


--- fbgen.c.orig Sat May 4 14:35:32 2002
+++ fbgen.c Sat May 4 15:02:37 2002
@@ -514,7 +514,8 @@
         if (con == info->currcon) {
                 if (info->fbops->fb_pan_display) {
- if ((err = info->fbops->fb_pan_display(&info->var, con, info)))
+ /* Tony: offsets are still in disp->var, not info->var */
+ if ((err = info->fbops->fb_pan_display(&fb_display[con].var, con, info)))
                                 return err;

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This archive was generated by hypermail 2b29 : Tue May 07 2002 - 22:00:22 EST