linux-kernel - RE: [PATCH v1] USB:gadget: Fix a warning while loading g_mass

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Date:	Thu, 5 Jun 2014 10:21:19 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Peter Chen <Peter.Chen@...escale.com>
cc:	"Yang,Wei" <Wei.Yang@...driver.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
	Felipe Balbi <balbi@...com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v1] USB:gadget: Fix a warning while loading g_mass_storage

On Thu, 5 Jun 2014, Peter Chen wrote:

> > > > It is a little strange we call gadget's disconnect at SET_ADDRESS?
> > > > How the udc calls gadget driver the disconnection has happened when
> > > > the usb cable is disconnected from the host?
> > > >
> > > > Usually, we call gadget's disconnect at two situations
> > > >
> > > > - udc's reset handler if udc's speed is not UNKNOWN, it is usually
> > > > happened when the host sends reset after enumeration.
> > > > - udc's disconnect handler, it is usually happened when the usb
> > > > cable is disconnected from host.
> > >
> > > Hmm, usually the two situations, but according to the commit log, s3c
> > > hsotg does not support Disconnected interrupt for device mode, so the
> > > second situation does not happen for s3c hsotg, therefore, he has to
> > > disconnect the connection before it is connected again.
> > 
> > Why does he need to do that?  Why not just skip the disconnect
> > notification if the hardware can't detect a disconnect?
> > 
> 
> We must call gadget driver's disconnect, otherwise, there at least
> has a warning when unload module, please refer to __composite_unbind
> at drivers/usb/gadget/composite.c

The disconnect callback can run just before unbind.  That's not a valid
reason for doing a disconnect notification as part of SET_ADDRESS.

Alan Stern

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