Rui-Xiang Guo wrote:

> > Xmame uses the heuristics that you need to move the joystick > half the
> > distance between center and max/min for it to detect it as a move event.
> > Center is taken as the value of the joystick when xmame starts (HID devices
> > do tell their center value in the descriptor, but this is not always
> > correct, especially for joystick -> USB adapters, so we cannot rely
> > on it.)
>
> In fact, I use the USB gamepad. Is it's behavior different from joystick?
>
> > So I cannot see how you get this behavior (provided that the joystick is
> > reasonable positioned when you start xmame...) It might be that your
> > joystick reports something that confuses the code. I'll take a look at
> > the code to see if I can find any strangness...
>
> I do not touch the gamepad before run xmame. :)
> After I start xmame, no matter what I do, like pushing a button,
> the guy in the xmame screen still will go to left automatically.
> I have tried to change the 'joy_data[i].axis[axis].center' value to be negative.
> It can got to right, but can't go back to left. X-)
> I also tried to calculate the 'physical center' value with
> physical_minimum and physical_maximum, and it is '127'.
> What does this value mean?

I did some changes in the code that determines the sign of a value in linusbhid,
maybe it's wrong.  (The spec says nothing about sign.)  What are the min and
max values?

    -- Lennart