On Tue, 13 Jun 2017, Felipe Balbi wrote:
>
> Hi Alan,
>
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> > Felipe:
> >
> > A UDC driver will invoke the gadget driver's ->disconnect callback
> > whenever the D+ pullup is turned off. During gadget driver unbinding,
> > this happens automatically when usb_gadget_remove_driver() calls
> > usb_gadget_disconnect().
>
> usb_gadget_disconnect() only calls UDC's ->pullup(), not gadget driver's
> ->disconnect()
>
> int usb_gadget_disconnect(struct usb_gadget *gadget)
> {
> int ret = 0;
>
> if (!gadget->ops->pullup) {
> ret = -EOPNOTSUPP;
> goto out;
> }
>
> if (gadget->deactivated) {
> /*
> * If gadget is deactivated we only save new state.
> * Gadget will stay disconnected after activation.
> */
> gadget->connected = false;
> goto out;
> }
>
> ret = gadget->ops->pullup(gadget, 0);
> if (!ret)
> gadget->connected = 0;
>
> out:
> trace_usb_gadget_disconnect(gadget, ret);
>
> return ret;
> }
> EXPORT_SYMBOL_GPL(usb_gadget_disconnect);
Yes, but as I mentioned above, the pullup routine calls the gadget
driver's disconnect method.
> > But immediately thereafter, usb_gadget_remove_driver() calls the gadget
> > driver's ->disconnect callback directly! Do we have any reason for
> > doing this? I don't see point to it. Should that call be removed?
>
> Unless I'm missing something, that call is necessary :-) Have you faced
> any issues with it? Are there any UDCs calling gadget driver's
> ->disconnect() from ->pullup() ?
I haven't faced any issues because gadget drivers don't seem to mind
->disconnect getting called twice in a row. :-) (And note that the
API doesn't have a corresponding ->connect callback... Although to
tell the truth, it's not clear what a gadget driver needs to do in
either callback. Can we simply remove ->disconnect altogether?)
Both dummy-hcd and net2280 call ->disconnect from ->pullup. I haven't
checked other UDC drivers, but it seems like something they should all
do. Except perhaps in the case where the UDC driver doesn't have a
pullup method.
Alan Stern
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