As for how to solve this? The module reference count will be incremented when the device is opened, right? Then on close, make sure all urbs are flushed out before finishing the close function. Unfortunatly, this seems to require keeping track of all pending urbs in flight, which is kind of the opposite for doing what the visor driver is doing...
There was some proposals for how to fix this in the past on the mailing list, but I don't think they ever went very far.
We now have lots of the necesary infrastructure, but backwards compatibility (for drivers) has been preventing a final step.
Specifically, drivers/usb/core/usb.c has usb_disconnect() trigger the driver disconnect() call ... and only AFTER that returns (and driver module might be rmmodded) will it disable() the endpoints.
For correctly functioning USB device drivers, disable() just means the HCD and HC handshake correctly. For malfunctioning drivers, which violate the long-standing "driver disconnect() must unlink all pending URBs" rule, disable() also forces still-pending URBs to complete ... potentially after the driver has been rmmodded.
It'd be simple, now that we have the endpoint disable capability, to change the semantics of disconnect(). Just disable all the endpoints BEFORE calling drivers' disconnect(): switch those two short blocks of code in usb_disconnect().
That's the model I used in the gadget API, and it made the interactions between the controller driver and the device (gadget) driver a LOT simpler during disconnect/rmmod.
IMO this change would be worth considering for 2.5 even at this late date, even though it'd break some TBD number of drivers.
Because the upside of that change would be that on 2.5, USB device driver disconnect() bugs would be less _able_ to break things in usbcore or elsewhere in the system. And there are a lot of driver disconnect() bugs that likely won't get fixed without some fundamental change like that.
- Dave
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