Am Sonntag, 12. Januar 2003 09:11 schrieb Greg KH:
> On Sat, Jan 11, 2003 at 11:39:55AM +0100, Oliver Neukum wrote:
> > Currently there's no way to tell an urb executing its completion handler
> > from a finished urb. So we wouldn't have to poll, but could wake the task
> > doing the unlink from usb_hcd_giveback_urb(). In fact we'd have to.
>
> Then why don't we finally fix this problem? Just give the urb a
> different status while in the completion handler, and then fix up a few
> drivers. It shouldn't be that hard :)
Sir, yes, sir!
To read is to obey ;-)
OK, if we are to do this let's do it right and divorce state from
error reporting.
As far as I can tell an URB should have four states, with preliminary names:
1 - URB_FREE
2 - URB_SUBMITTED
3 - URB_COMPLETING
4 - URB_CANCELED
with the following transitions allowed:
1->2, 2->3, 3->1, 3->2, 3->4, 4->1
usb_alloc_urb() will make you an URB in state URB_FREE
transition 1->2: usb_submit_urb() after sanity checking
transition 2->3: usb_hcd_giveback_urb() before complete
transition 3->1: usb_hcd_giveback_urb() after complete
transition 3->2 (resubmit in completion handler): same as 1->2
transition 3->4: usb_unlink_urb(), if a synchronous unlink is called for an
URB in state URB_COMPLETING
transition 4->1: usb_hcd_giveback_urb() after complete
The interesting change is the state URB_CANCELED which
causes usb_submit_urb() to fail and usb_hcd_giveback_urb() to wake up
the thread having done a synchronous unlink.
Should asynchronous unlink remain unchanged?
Or should it change the urb into state URB_CANCELED and just
not wait?
Do we have to guarantee that usb_submit_urb() returns before
the completion handler is called?
Regards
Oliver
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