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SubjectRe: [RFC PATCH 2/3] usb: typec: Add product_type sysfs attribute file for partners and cables
Hi Benson,

On Wed, Nov 18, 2020 at 09:48:21AM -0800, Benson Leung wrote:
> > +What: /sys/class/typec/<port>-partner/product_type
> > +Date: December 2020
> > +Contact: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > +Description: USB Power Delivery Specification defines a set of product types
> > + for the partner devices. This file will show the product type of
> > + the partner if it is known. Dual-role capable partners will have
> > + both UFP and DFP product types defined, but only one that
> > + matches the current role will be active at the time. If the
> > + product type of the partner is not visible to the device driver,
> > + this file will not exist.
> > +
> > + When the partner product type is detected, or changed with role
> > + swap, uvevent is also raised that contains PRODUCT_TYPE=<product
> > + type> (for example PRODUCT_TYPE=hub).
> > +
> > + Valid values:
> > +
> > + UFP / device role
> > + ======================== ==========================
> > + undefined -
> > + hub PDUSB Hub
> > + peripheral PDUSB Peripheral
> > + psd Power Bank
> > + ama Alternate Mode Adapter
> > + vpd VCONN Powered USB Device
>
> I have it on good authority that "vpd" is incorrectly categorized here,
> and for future proofing, we'd better not introduce vpd as a product
> type for UFP...
>
> A vpd is actually more closely related to a "cable" than it is a "UFP."
> A closer reading of the USB Type-C and USB PD specs will reveal that
> VPDs can only ever appear as SOP' and not as SOP, so having its type
> appear under UFP is a mistake.
>
> In other words, the USB PD V3.0 R2.0 spec is wrong. A change has been
> working its way through the spec committee to fix this, but it is not yet
> published.
>
> In order to reduce the amount of churn, I would recommend not
> including vpd as a possible type until a new version of the spec (or the ECN)
> is published.

Thanks for the heads-up. I'll leave the vpd out then.

cheers,

--
heikki

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