Re: [PATCH] usb: typec: Defer checking of valid power role swap to low level drivers

[Guenter Roeck]

On 05/17/2017 12:34 AM, Oliver Neukum wrote:
> Am Mittwoch, den 17.05.2017, 00:32 -0700 schrieb Badhri Jagan
> Sridharan:
>
> Hi,
>
> > "Two independent set of mechanisms are defined to allow a USB Type-C
> > DRP to functionally swap power and data roles. When USB PD is
> > supported, power and data role swapping is performed as a subsequent
> > step following the initial connection process. For non-PD implementations,
> > power/data role swapping can optionally be dealt with as part of the initial
> > connection process."
>
> Well, as I read it, without PD once a connection is established, you
> are stuck with your role. So it seems to me that blocking a later
> attempt to change it makes sense.

That seems to be a harsh and not very user friendly reading of the specification.

I would argue that the user doesn't care if the partner supports PD or not
when selecting a role, and I would prefer to provide an implementation which is
as user friendly as possible.

Thanks,
Guenter