linux-kernel - Re: [PATCH 1/3] usb: USB Type-C Connector Class

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Message-ID: <20160218084724.GA1859@kuha.fi.intel.com>
Date:	Thu, 18 Feb 2016 10:47:24 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Oliver Neukum <oneukum@...e.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...nel.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 1/3] usb: USB Type-C Connector Class

Hi Oliver,

On Wed, Feb 17, 2016 at 03:07:27PM +0100, Oliver Neukum wrote:
> On Tue, 2016-02-09 at 19:01 +0200, Heikki Krogerus wrote:
> > 1. connected - Connection status of the connector
> > 2. alternate_mode - The current Alternate Mode
> > 3. alternate_modes - Lists all Alternate Modes the connector supports
> > 4. partner_alt_modes - Lists partner's Alternate Modes when connected
> 
> Now that I think about it, there's a gap.
> Which SVIDs do we expose if we are UFP (slave)?

In the alternate_modes listing the connectors alt modes, we can not
have modes that the hardware can not support of course, and it is the
responsibility of the drivers registering the type-c ports with this
clss to make sure they are not part of the list.

In partner alternate modes, we will list all alternate modes the
partner supports, even the ones our connector doesn't.

The modes that can actually be selected have to be supported by both
the connector and the partner, and this is where I'm putting the ball
on the userspace at the moment. I'm not offering a list of
"possible_alternate_modes" where I list the combination, but instead
expect the userspace to be figure out that on it's own.

Do you think we should add "possible_alternate_modes" file?

P.S. That reminds me, here's my current draft for the
Documentation/ABI/. Could you take a look?

Thanks,

-- 
heikki

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