linux-kernel - Re: [PATCH 3/4] USB: serial: add support for multi-interface functions

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Date:   Wed, 31 Mar 2021 13:21:15 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] USB: serial: add support for multi-interface
 functions

Am Mittwoch, den 31.03.2021, 09:08 +0200 schrieb Oliver Neukum:
> Am Dienstag, den 30.03.2021, 17:22 +0200 schrieb Johan Hovold:
> > On Tue, Mar 30, 2021 at 04:44:32PM +0200, Oliver Neukum wrote:
> > > Am Dienstag, den 30.03.2021, 16:38 +0200 schrieb Johan Hovold:
> > > > @@ -1115,6 +1161,8 @@ static void usb_serial_disconnect(struct usb_interface *interface)
> > > >         if (serial->type->disconnect)
> > > >                 serial->type->disconnect(serial);
> > > >  
> > > > +       release_sibling(serial, interface);
> > > > +
> > > >         /* let the last holder of this object cause it to be cleaned up */
> > > >         usb_serial_put(serial);
> > > >         dev_info(dev, "device disconnected\n");
> > > 
> > > Hi,
> > > 
> > > does this assume you are called for the original interface first?
> > 
> > No, I handle either interface being unbound first (e.g. see
> > release_sibling()).
> > 
> > > I am afraid that is an assumption you cannot make. In fact, if somebody
> > > is doing odd things with sysfs you cannot even assume both will see a
> > > disconnect()
> > 
> > Right, but disconnect() will still be called also for the sibling
> > interface as part of release_sibling() above.
> 
> OK, sorry I overlooked that.

Hi,

on the third hand, the more I look at this, would you mind putting
sibling_release() with a modified name into usbcore? This functionality
is not limited to serial drivers. btusb needs it; cdc-acm needs it;
usbaudio neds it. We have code duplication.

	Regards
		Oliver