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

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Date:	Mon, 23 May 2016 17:55:04 +0200
From:	Oliver Neukum <oneukum@...e.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...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 Mon, 2016-05-23 at 07:43 -0700, Guenter Roeck wrote:
> On 05/23/2016 06:58 AM, Oliver Neukum wrote:

> > Now I am confused. Are you saying that the choice of Alternate Mode does
> > not belong into user space?
> >
> 
> No; sorry for the confusion. The above was meant to apply to my use
> of "preferred mode", not yours. I was trying to say that the choice of
> preferred roles (which determines if Try.SRC or Try.SNK is enabled)
> should belong primarily into the kernel, to be determined by the platform
> (presumably via ACPI, devicetree data, or platform data). If it should

Why on earth? That is most clearly a policy decision.

> be possible to override it by user space is a different question. That
> might be useful, at least for testing. If so, does such an override
> belong into the class or into the PD driver ? Good question. I am fine
> either way.

Well, if platform data has a default, I suppose we ought to use it.

> I don't really have a strong opinion about alternate mode selection. I would
> think that there should be a kernel (platform) default, possibly determined
> by the alternate mode itself, but I also think that it should be selectable
> by user space. Question is if that should be done through the alternate mode
> driver or through the class (example: alternate modes used for firmware

I would say that the ought to be a driver for type C which controls
alternate modes and roles.

	Regards
		Oliver