kdrive rotation problems

[Ezio Baldinotti]

Using X11R7.3 X.org release, I experienced the following issue.

Everything works fine if I run the server with:
Xfbdev -keybd keyboard,device=/dev/input/event1 -mouse
tslib,,device=/dev/input/event0

Instead, when I rotate the screen with:
Xfbdev -screen 240x320 at 90 -keybd keyboard,device=/dev/input/event1
-mouse tslib,,device=/dev/input/event0

The Y coordinate is correctly managed, while the X remains stuck at
0...

Any suggestion will be appreciated.
Thanks,
Ezio Baldinotti