On Fri, Aug 13, 2010 at 09:51:33AM -0700, Greg KH wrote:
> On Fri, Aug 13, 2010 at 06:24:37PM +0200, Hans Petter SELASKY wrote:
> > Hi Greg,
> >
> > We have been thinking about various ways to solve this problem.
> > Another way is to re-program then endpoint number to an invalid
> > endpoint, but that will only work as long as there is an unused
> > endpoint. It appears that the host mode has not been too well tested
> > on the MUSB chips. The existing code works because classes like the
> > mass storage host driver don't cancel URB's, but rather wait for them
> > to complete or timeout. We've seen this issue when testing the USB
> > modem host class on Linux using an embedded board, that if the peer is
> > not fast enough to read the TX'ed data, we get in the situation where
> > the already existing warning triggers during modem port close, and the
> > chip goes into a non-responding state. We have not been able to get
> > any confirmation from hardware people about this issue.
>
> How about we wait until you do get confirmation from the hardware
> people? That would make more sense, right?
>
> > Yes, it's bad to affect all Linux USB users.
>
> That's my main worry.
>
> > Another way is to have an
> > USB API where we can set a bit in the USB-device-map bit-array when we
> > are attaching the MUSB driver, so that the Linux USB stack always sees
> > address X, like in use. That would probably be better, but adds more
> > code. Could you add such an API to the USB core. For example:
> >
> > int
> > usb_reserve_bus_address(bus, addr)
> > {
> > ...
> > return 0; /* success */
> > }
>
> We could, but I'll have to go dig through my usb spec to verify that we
> are allowed to do such a thing. For some reason I thought we were
> required to support all 128 devices.
Ok, in looking through the USB spec again, it looks like we just can't
send an address greater than 127 to a device, nor a 0. So we could
reserve one number for broken hardware like this, but I would really
like it if there was some other way to mark this device as "broken".
thanks,
greg k-h
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