Re: [PATCHv11 2/3] usb: USB Type-C connector class

From: Greg KH
Date: Mon Nov 21 2016 - 09:45:01 EST

On Mon, Nov 21, 2016 at 03:11:03PM +0200, Heikki Krogerus wrote:
> Hi Greg,
> On Mon, Nov 21, 2016 at 11:35:28AM +0100, Greg KH wrote:
> > > +static void typec_partner_release(struct device *dev)
> > > +{
> > > + struct typec_port *port = to_typec_port(dev->parent);
> > > +
> > > + typec_unregister_altmodes(dev);
> > > + port->partner = NULL;
> > > +}
> >
> > This doesn't feel right, why are you both exporting
> > typec_unregister_altmodes() and also calling it from release callbacks?
> > That implies there is two way to clean stuff up, so what is a driver
> > writer to use? Please simplify and force it to be one way or the other.
> OK.
> > Also typec_unregister_altmodes() doesn't free memory, which release is
> > supposed to be doing, which also implies that the reference counting
> > logic is all wrong here. Please fix, like I asked you to previously.
> There is nothing wrong with the reference counting, and nothing has
> been allocated so there is nothing to free.

The device structure itself that this release call is for needs to
be freed, right? If not, something is really wrong...

> Please note that the partner device is meant to just represent the
> partner in user space and not to be actually used for anything. And
> please also note that there can only be one partner for a port at a
> time.

Ok, but these are still reference counted devices, you need to handle
that properly.

> We could allocate an extra structure for the partner when
> typec_connect() is called, but we would do that just for the sake of
> having something to free in the release hook. It would not be useful
> for anything. It would not help us increase/decrease the reference
> count of the device, and the port driver would still have to provide
> details about the partner capabilities the moment it tells us the
> partner was connected.

Again, free the device for which this release function is being called
for, that is why it is there.


greg k-h