RE: [linux-usb-devel] Re: USB, HID, unexpected disappearances

[Dunlap, R. <ran...@in...>]

> From: Franz Sirl [mailto:Fra...@la...]
> 
> At 08:30 20.07.00, Alexander Perry wrote:
> >If someone jiggles the USB cables while a USB
> >joystick is in active use, the stack may detect
> >this as the device being dropped and reattached.

Sounds like a cable/device problem to me.

> >In this case, we have no idea whether it is the
> >same device, so we naturally take the next free
> >device number.  That's fine by me; I see it happen.

Is the device disconnected and dropped, or just
dropped without being disconnected (as far as the
USB stack knows)?  If the USB stack does a disconnect
for the device and then another connect happens,
the connected device will be assigned the same
device number.  Or is this happening too quickly
for that to happen?

> >Unfortunately, the FD that is reading the existing
> >device number doesn't generate any errors, and simply
> >keeps repeating the old data back indefinitely.
> >The application has no reason to suspect anything
> >has gone wrong, and cheerfully lets the game
> >continue running with frozen user controls.
> >
> >If an error would be returned, at least the application
> >might be able to act (even if only to abort the game
> >in progress).  In the case of FlightGear, I was planning
> >to have it search for new joysticks so that it can find
> >the new device number and continue to accept input data.
> >There might be a fraction of a second glitch in the
> >control response while this occurs, but that would be
> >much less irritating that the existing behavior.
> >
> >Is the lack of an error a consequence of a spec that
> >we're obeying, or can it easily be changed please ?

> I noticed that too, and there was a short discussion recently on the 
> linuxconsole-dev list about that.

So linux-console discusses USB also?  Man, I have too much
email already.  :(

~Randy