On Tue, 23 May 2006, Franck Bui-Huu wrote:
> ok so the code can be rewritten as following:
>
> clear_bit(US_FLIDX_URB_ACTIVE, &us->flags);
> if (timeout <= 0) {
> US_DEBUGP("%s -- cancelling URB\n", !timeout ?
> "Timeout" : "Signal");
> usb_unlink_urb(us->current_urb);
> }
Yes, except for the unlikely (but not impossible) case where the URB
gets aborted and unlinked just as the timeout expires. Then you would try
to unlink it a second time, which wouldn't hurt anything.
> > Come to think of it, the code always needs to wait until the URB has
> > completed. So after you call usb_unlink_urb, you need another
> > wait_for_completion -- non-interruptible and with no timeout.
>
> It seems to be needed for _all_ drivers. A generic service provided by the
> core
> which unlinks an urb _and_ waits for its completion...maybe we should start a
> new thread for that...
There already is such a service. It's called usb_kill_urb. It has
slightly higher overhead than usb_unlink_urb + wait_for_completion, but
since this is a low-probability error pathway that doesn't matter.
Alan Stern
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