[Libdlo] More notes Xorg 1.9

[Christoph Rissner]

Hi all,

I've had some more time to play with various configurations of 
fbdev/displaylink and nvidia under Xorg 1.9.

The most interesting thing is that I found out why I can use the 
displaylink driver together with nvidia but not the fbdev driver.

This is just an explicit check (xf86Bus.c, xf86PostProbe()) whether both 
framebuffer and pci devices have been claimed, if so the server refuses 
to start.
The displaylink driver just clears the corresponding fbSlotClaimed flag, 
no more magic required. But, there is another (similar) check in 
xf86ClaimFbSlot() (xf86fbBus.c) that, when claiming a frambuffer slot, 
makes sure no PCI slot has been allocated, I guess thats the reason why 
the displaylink driven device must be registered first (as primary screen).

As I wanted to test the fbdev driver (as Bernie suggested in another 
thread), I just removed those fb-vs-pci checks from the X server, and 
hey, it works. I'm pretty sure this test has a reason, but as long as it 
works I'm willing to patch my X server.

Another thing I appreciate is that I no more have to hardcode the 
Xinerama layout (I used to patch libxinerama), something in 
Xserver-libxinerama-nvidia changed such that my screen configuration is 
correctly recognized.

Thats the good(?) news, but I'm still not completely satisfied, at least 
not so much to upgrade my "main" workstation.

As noted in 
http://lists.freedesktop.org/archives/libdlo/2010-November/000806.html, 
my X server crashes when running twm on Xinerama, it's no difference 
whether I use fbdev or displaylink drivers (and whether I use my patched 
xorg-server or a vanilla version with displaylink). As soon as I click 
on a window title bar (or try to move it otherwise), X crashes. Funny 
thing, since I can resize the windows and/or just use it (xterm, 
firefox), but as soon as I try to move it ...

Using e17 as WM is fine, moving, resizing, no crashes there. But, and I 
have no idea where that comes from, when I move some window across a 
monitor boundary, the udlfb screen goes all black and comes back after 1 
or 2 seconds, working again. It's the same when dragging the window 
from/to the udlfb monitor or across a boundary on my other device.
Any thoughts how I might fix that?
This is the main reason for me to stay on Xorg 1.8/displaylink.

Thanks,
Christoph