linux-kernel - Re: [PATCHv3 1/2] usb: USB Type-C connector class

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Message-ID: <CAOiXhaJPe1LnQ2YUTSET-nvQsgTx=SHiJ=DTQFehJ3usmcQ3UA@mail.gmail.com>
Date:	Wed, 29 Jun 2016 14:21:10 +0530
From:	Rajaram R <rajaram.officemail@...il.com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Oliver Neukum <oneukum@...e.com>,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCHv3 1/2] usb: USB Type-C connector class

On Mon, Jun 27, 2016 at 5:43 PM, Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
> Hi,
>
> On Mon, Jun 27, 2016 at 03:51:08PM +0530, Rajaram R wrote:
>> May be I am missing user or usage of the driver.. I see this driver is
>> providing limited information of the Type-C connectors or the port
>> partner
>
> Yes, this interface can't provide directly information received from
> PD commands like Discover Identity. We will have to present the
> partners even when USB PD is not supported and in a consistent
> fashion. Some details will be available in any case indirectly. Like
> if there are modes, there will be devices presenting them, and the
> product type in case of partners will be the partner type.

Agree. What is the end use of this driver? IMO end use case will
decide what attributes to be shared.  Since we are terming this as a
universal representation for user space we may need to expose details
such as Discovery details say Vendor ID, Product ID, Super Speed
support etc which are not related to alt mode.  In the legacy drivers
complete descriptors of the device is available for user space to
build applications.

>
> But there are a couple of attributes I have been thinking about adding
> for the partners:
>
>         supported_data_roles
>         supports_usb_power_delivery
>
> The supported data roles would respond bits 30 and 31 of the ID Header
> VDO. But when the partner does not support USB PD, we will have to
> report "unknown" in it.
>
> Oliver, Guenter! How do you guys feel about those? Is there any use
> for them?
>
>
>> On Mon, Jun 27, 2016 at 3:21 PM, Heikki Krogerus
>> <heikki.krogerus@...ux.intel.com> wrote:
>> > On Fri, Jun 24, 2016 at 07:54:12PM +0530, Rajaram R wrote:
>> >> On Tue, Jun 21, 2016 at 8:21 PM, Heikki Krogerus
>> >> <heikki.krogerus@...ux.intel.com> wrote:
>> >> > The purpose of USB Type-C connector class is to provide
>> >> > unified interface for the user space to get the status and
>> >> > basic information about USB Type-C connectors on a system,
>> >>
>> >> Since we are defining this is as a unified interface for user space,
>> >> will the interface include identity details of local port and peer.
>> >> Or am I over looking something ?
>> >
>> > By peer, do you mean the partners? Sorry but could you elaborate the
>> > question?
>
>
> Thanks,
>
> --
> heikki