linux-kernel - Re: [PATCH 0/3] usb: USB Type-C Class and driver for UCSI

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Message-ID: <20160218092151.GB1859@kuha.fi.intel.com>
Date:	Thu, 18 Feb 2016 11:21:51 +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 0/3] usb: USB Type-C Class and driver for UCSI

On Wed, Feb 17, 2016 at 07:53:47PM +0100, Oliver Neukum wrote:
> On Tue, 2016-02-09 at 19:01 +0200, Heikki Krogerus wrote:
> > Hi,
> > 
> > The OS, or more precisely the user space, needs to be able to control
> > a few things regarding USB Type-C ports. The first thing that must be
> > allowed to be controlled is the data role. USB Type-C ports will
> > select the data role randomly with DRP ports. When USB PD is
> > supported, also independent (from data role) power role swapping can
> > be supported together with Alternate Mode control.
> 
> What about S4? We need to restore the alternate mode upon resume,
> if we are the DFP and as that might involve storage devices it
> needs to be done in kernel space.

That I'm expecting to be the responsibility of the drivers registering
the ports at them moment, because I'm afraid of all the possible
different kind of platform specific oddities that need to be
considered.

But I guess all we would need to do in the class is store the roles
and mode during suspend, and restore them during resuming with
dr_swap, pr_swap and set_alt_mode hooks if they changed.


Thanks,

-- 
heikki