Re: [PATCHv6 1/3] usb: USB Type-C connector class
From: Heikki Krogerus
Date: Mon Aug 29 2016 - 09:43:13 EST
On Mon, Aug 29, 2016 at 06:04:52AM -0700, Guenter Roeck wrote:
> On 08/26/2016 07:07 AM, Heikki Krogerus wrote:
> > > > > > +What: /sys/class/typec/<port>-partner/type
> > > > > > +Date: June 2016
> > > > > > +Contact: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > > > > > +Description:
> > > > > > + Shows the type of the partner. Can be one of the following:
> > > > > > + - USB - When the partner is normal USB host/peripheral.
> > > > > > + - Charger - When the partner has been identified as dedicated
> > > > > > + charger.
> > > > > > + - Alternate Mode - When the partner supports Alternate Modes.
> > > > > > + - Accessory - When the partner is one of the accessories with
> > > > > > + specific Accessory Mode defined in USB Type-C
> > > > > > + specification.
> > > > >
> > > > >
> > > > > where a dock would be classified ?
> > > >
> > > > A dock is just USB PD capable device with a bunch of alternate modes
> > > > that is attached to the port. There is no specific identifier for a
> > > > "dock".
> > >
> > > My remark was a bit too stern,
> > > I meant a dock might be 'USB' 'Charger' 'Alternate Mode' , all at the
> > > same time or alternately depending what you plug in.
> > > I don't really see those types as mutually exclusive.
> > So USB type means the partner does not have alternate modes (I'll
> > clear that in the documentation), Charger is a dedicated charger and
> > therefore can not be anything else (no USB, no alternate modes).
> This is probably the most difficult attribute to support.
> Many PD capable chargers support alternate modes (for firmware upgrades).
> As I mentioned earlier, it is difficult to match reported Type-C partner
> types (or really anything reported in the SVDM Identity command)
> to the above types.
> Does it really make sense to deviate that much from the Type-C specification ?
> I can understand why you hesitate to use DFP / UFP, as those terms are
> really hard to understand for the non-initiated. However, here it is really
> difficult to even determine which value to set. The best I can come up with is
> - Not PD capable. Report USB (obviously includes non-PD capable chargers)
> - PD capable, supports alternate modes. Report as Alternate Mode (including
> PD chargers supporting alternate modes)
> - PD capable, does not support alternate modes. Report as Accessory if
> connected as accessory, as charger if we the port is connected as sink,
> USB otherwise
> Overall this is quite vague and, especially for chargers, most of the time
> misses the point.
> I would really prefer if we could stay closer to the specification in this
> case, and not try to merge multiple orthogonal attributes into one.
OK. So what would you propose?