On Tue, Jun 13, 2017 at 10:22:26AM -0400, Alan Stern wrote:
> On Tue, 13 Jun 2017, Felipe Balbi wrote:
>
> >
> > Hi Alan,
> >
> > Alan Stern <st...@rowland.harvard.edu> 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.
>
No, ->pullup is expected to be called from UDC core, and the UDC core
makes sure the coming ->disconnect at kinds of situations.
--
Best Regards,
Peter Chen
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