On Mon, 24 Aug 2015, Peter Chen wrote:
> Thanks, that's much clear.
>
> At udc driver:
>
> __set_halt(struct usb_ep *ep, int value, bool may_fail)
> {
> if (may_fail && ep queue is not empty) {
> return false
> } else {
> do stall;
> return true;
> }
> }
>
> gadget_ops:
> .set_halt = ep_set_halt,
>
> ep_set_halt(struct usb_ep *ep, int value)
> {
> __set_halt(ep, value, true);
> }
>
> And call __set_halt(ep, value, false) at below conditions:
> - SET(CLEAR)_FEATURE for Set(Clear)-Halt
> - If ep0 request has failed
Yes, that should work. In fact, when a control request fails, you
could even call ep_set_halt instead of __set_halt, because the ep0
queue will certainly be empty.
> Do we need to update kernel doc for usb_ep_set_halt that
> say it should only for bulk and interrupt endpoints?
I don't think we need to change it. The USB spec says that isochronous
endpoints never stall; section 5.6.5 says:
An endpoint for isochronous transfers never halts because there
is no handshake to report a halt condition.
Also, Figure 8-39 does not include any STALL packets.
Lastly, usb_ep_set_halt should be called for ep0 when the gadget is
unable to respond to a request.
Alan Stern
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