Re: Joystick not found on Linux/amd64

[Joshua Wise <joshua@joshuawise.com>]

Bernhard Ager wrote:
> Hello,
> 
> I just tried out version 8.03 of X-Plane for Linux. Works really smoothly 
> for me, except that the joystick is not found :-( The joystick 
> itself should be working, as e.g. jstest tells me: 
> 
> Joystick (Analog 4-axis 4-button joystick) has 4 axes and 4 buttons. Driver version is 2.1.0.
> 
> The issue might be, that I am using Linux on the amd64 architecture and 
> letting run X-Plane in the 32bit "emulation", though I can't really see 
> why.
I've had a report of this problem in the past. I have a vague 
understanding of why it happens, but I'm not sure how to fix it.

As far as I can tell, the problem is that my code uses the joystick 
ioctls to get the version, passing it a 32-bit address to return the 
version into. This doesn't work out so hot in the 64-bit kernel, which 
decides that my 32-bit address is full of crap, and gives me an errno of 
-EFAULT, which means that I passed it a bad address. My code handles 
this by not detecting the joystick at all, thinking that the version is 
too old, since the kernel didn't change it.

So, basically, I think I know why it happens, but I'm not certain 
whether its my code at fault or the kernel's. This is a good question. 
I'm going to cc: this to LKML, in the hope that somebody there can 
provide some insight.

I am not subscribed to LKML - anyone on there who is responding, please 
cc: me in your responses.

joshua