On Sun, 26 Mar 2006, Franck Bui-Huu wrote:
> I got 2 more questions, hope you don't mind.
>
> Can I assert that the ep0's request queue has always one request queued ?
No, of course not. Most of the time there won't be any requests queued.
On ep0, requests are queued only in response to Setup packets from the
host.
> Is it safe when aborting all requests of an ep's queue to do
>
> while (queue is not empty) {
> request = first request of the queue
> remove_request_from_queue(request);
> driver->complete(request, status = -ERROR);
> }
>
> I mean, am I sure that the driver won't queue another request to the queue ?
No, you can't be sure of that. But if the gadget driver does queue
another request, it has to take the consequences. In these circumstances
it's not defined whether the new request would also get aborted.
So yes, that is a workable algorithm. If instead you tried to do this:
lastreq = last request of the queue
while (queue is not empty) {
request = first request of the queue
dequeue(request)
driver->complete(request, status = -ERROR);
if (request == lastreq)
break;
}
then you run the risk of the gadget driver deleting lastreq by itself,
before you do. Hence you might as well stick to the simpler algorithm.
Alan Stern
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