Re: X screen wraps around

[Duncan Sands <duncan.sands@math.u-psud.fr>]

On Fri, Jun 08, 2001 at 08:13:21PM +0200, Michel Daenzer wrote:
> Duncan Sands wrote:
> > 
> > > > I am running X 4.0.3 on an 8500 powermac (controlfb), kernel 2.4.
> > > > If I use 8bpp all is well (kernel parameter:
> > > > video=controlfb:vmode:14,cmode:0).
> > >
> > > Well, I guess this answers most of the questions in my other post...
> > 
> > Sorry about that!
> 
> No worries, I could have looked at your other post before asking.
> 
> 
> > > I thought I had fixed this for 4.0.2 already, but it only works reliably
> > > with ShadowFB enabled, which is the default though - you don't happen to
> > > disable it explicitly?
> > 
> > Nope:
> 
> Hmm. The fbdevhw layer gets the framebuffer offset from the framebuffer
> device. That code used to be buggy before 4.0.2, but Geert helped me fix it.
> But this sounds like it isn't 100% correct yet. :(
> 
> Curious: Approximately by how many pixels is the picture shifted?

I did some experiments (X 4.0.3, kernel 2.4.5-pre3).  A negative screen
offset means that something that should be on the left appears on the
right, a positive offset means that something that should be on the
right appears on the left.

WITH kernel parameter video=controlfb:vmode:14,cmode:0

Depth 8		Result: screen position ok
Depth 15	Result: screen off by -13 or -14 pixels
Depth 16	Result: screen off by -13 or -14 pixels, colours no good
Depth 24	Result: fails (see note 1 below)
Depth 32	Result: fails (see note 2 below)

withOUT kernel parameter video=controlfb:vmode:14,cmode:0

Depth 8		Result: screen off by about +22 pixels
Depth 15	Result: screen position ok
Depth 16	Result: screen position ok, colours no good
Depth 24	Result: fails (see note 1 below)
Depth 32	Result: fails (see note 2 below)

Note 1: X fails to start.  Find the following in the log:
Depth 24 pixmap format is 32 bpp
Fatal server error
AddScreen/ScreenInit failed for driver 0

Note 1: X fails to start.  Find the following in the log:
FBDev(0): Depth 32. (--) framebuffer bpp 32
FBDev(0): Weight given (000) is inconsistent with the depth (32)


I don't recall getting failures for depths 24 and 32 before, but
it was a long time since I last tried them, and I've changed X
versions since then.

By the way, since depth 15 with no kernel parameter seems to work
fine, my problem is solved (though the bug is not fixed)!

Duncan.