> From: Felipe Balbi [mailto:[email protected]] > Sent: Wednesday, March 06, 2013 11:52 PM > > On Wed, Mar 06, 2013 at 11:26:08PM +0000, Paul Zimmerman wrote: > > > From: Felipe Balbi [mailto:[email protected]] > > > Sent: Wednesday, March 06, 2013 12:05 AM > > > > ... > > > > > looking at that loop, is it really necessary ? I mean, what you do is: > > > > > > spin_lock_irqsave(); > > > > > > while (!list_empty(list) && retry--) { > > > if (!retry) { > > > spin_unlock_irqrestore(); > > > boom(); > > > } > > > > > > spin_unlock_irqrestore(); > > > usleep_range(); > > > spin_lock_irqrestore(); > > > } > > > > > > are you really relying on that race to cleanup your qH list ? Doesn't > > > look to me that usleep is at all necessary here. > > > > Hi Felipe, > > > > ehci-hcd, ohci-hcd, and uhci-hcd all spin in their endpoint_disable > > functions too, so yes, I'm pretty sure it's necessary ;) > > I'm asking because there are no checks in this loop to make sure what > you're waiting for has happened. Unlinke the others you mention where > they either wait for a particular event with wait_for_event() or they go > back to a point where they check the HW conditions again.
"while (!list_empty(&qh->qtd_list) && retry--)" is waiting for the QTDs attached to the QH to be completed. The completions are done in the interrupt handler. Once all QTDs are completed, qh->qtd_list will be empty and the loop will exit. -- Paul -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
