linux-kernel - Re: [RFC PATCHv2] usb: USB Type-C Connector Class

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Date:	Tue, 21 Jun 2016 15:08:52 +0200
From:	Oliver Neukum <oneukum@...e.com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCHv2] usb: USB Type-C Connector Class

On Thu, 2016-05-19 at 15:44 +0300, Heikki Krogerus wrote:
> The purpose of this class is to provide unified interface for user
> space to get the status and basic information about USB Type-C
> Connectors in the system, control data role swapping, and when USB PD
> is available, also power role swapping and Alternate Modes.

This raises two more questions.

1. Booting

It is possible that our only display and, worse, our source
of power is a display that can be used only in an alternate mode
and is connected via a type C connector.

We need some kind of boot time support for alternate modes.

The firmware will surely want to display something. So it is possible
that we start the OS will a valid power contract. How do we deal
with that? Renegotiate?

2. Multiple GPUs

How do we know which GPU is connected to which port?

	Regards
		Oliver