Re: [PATCHv14 2/3] usb: USB Type-C connector class

[Guenter Roeck]

On 01/10/2017 12:54 AM, Heikki Krogerus wrote:
> Hi Guenter,
>
> On Mon, Jan 09, 2017 at 08:59:32AM -0800, Guenter Roeck wrote:
> > > +/**
> > > + * typec_register_partner - Register a USB Type-C Partner
> > > + * @port: The USB Type-C Port the partner is connected to
> > > + * @desc: Description of the partner
> > > + *
> > > + * Registers a device for USB Type-C Partner described in @desc.
> > > + *
> > > + * Returns handle to the partner on success or NULL on failure.
> > > + */
> > > +struct typec_partner *typec_register_partner(struct typec_port *port,
> > > +					     struct typec_partner_desc *desc)
> > > +{
> >
> > With the changes to hide the actual partner structure, this looks at first
> > glance like a minor API change, but it is substantial.
> >
> > Reason is that the vdo as required by typec_partner_desc is provided by a VDM
> > command reply, which is completely orthogonal to the PD registration process.
> > So far I was able to set the vdo later, after registering the connection,
> > and after (and if) the vdo was received.
>
> If the identity vdo value is updated after the creation of the device,
> then the user space needs to be notified separately.
>
> > Since the partner may not even respond to the DISCOVER_IDENT message, or not
> > support PD at all, this means that I would have to disconnect partner
> > registration from the PD protocol itself and tie it to the VDO message
> > exchange, with appropriate timeouts to register anyway even if the identity
> > was not received after some period of time or if the partner does not support
> > PD.
> >
> > This in turn means that I'll have to re-implement and possibly re-architect
> > a substantial amount of code.
>
> We don't need to protect the structures like this, we can change this
> back. But how about we introduce driver callback function for updating
> the value instead, which would also notify the uses space?

That would work.

Thanks,
Guenter