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

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Date:	Tue, 28 Jun 2016 16:12:41 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Rajaram R <rajaram.officemail@...il.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	Oliver Neukum <oneukum@...e.com>
Subject: Re: [PATCHv3 1/2] usb: USB Type-C connector class

On Mon, Jun 27, 2016 at 06:39:46AM -0700, Guenter Roeck wrote:
> On 06/27/2016 05:13 AM, Heikki Krogerus 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.
> > 
> > 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.
> > 
> 
> Or make the attribute invisible in that case.

Well, why not. I did not like the idea of hiding an attribute
previously. I preferred to have an attribute always available, unless
there was a single and clear way to determine the cases where any of
the attributes for example with our partners would be visible or not..
But who cares.

> > Oliver, Guenter! How do you guys feel about those? Is there any use
> > for them?
> > 
> Definitely good for debugging and informational. On the top of my head,
> I don't immediately see what a user would do with it, though, but then
> it would not hurt either to have the information.
> 
> I keep wondering if it would make sense to directly expose the ID header
> VDO, similar to the alternate mode VDOs, in the partner node.

Yes, it makes sense. I'll add an attribute for that.

But since you proposed hiding the attributes, I'll add an attribute
"supports_usb_power_deliver" in any case, and make the vdo attribute
visible only if it returs 1. I'll also make the "accessory" attribute
visible only in case the partner type is accessory.


Thanks Guenter,

-- 
heikki