linux-kernel - Re: [PATCH v10 2/7] usb: mux: add generic code for dual role port mux

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Message-ID: <5753E6FF.5010501@linux.intel.com>
Date:	Sun, 5 Jun 2016 16:46:55 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Jun Li <jun.li@....com>, Peter Chen <hzpeterchen@...il.com>
Cc:	"felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lee Jones <lee.jones@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Roger Quadros <rogerq@...com>
Subject: Re: [PATCH v10 2/7] usb: mux: add generic code for dual role port mux

Hi,

On 06/05/2016 04:33 PM, Jun Li wrote:
>> Port mux is part of dual role switch, but not the whole thing.
>> > 
>> > Dual role switch includes at least below things:
>> >  - ID or type-C event detection
>> >  - port mux
>> >  - VBUS management
>> >  - start/stop host/device controllers
>> > 
>> > An OTG/Dual-role framework can be used to keep all these things run
>> > together with an internal state machine. But it's not duplicated with a
>> > generic framework for port mux and the port mux drivers.
>> > 
>>> > > Your
>>> > > case is just like Renesas case, which uses two different drivers
>>> > > between peripheral and host[1].
>> > 
>> > In my case, the port mux devices are physical devices and they can be
>> > controlled through GPIO pins or device registers. They are independent of
>> > both peripheral and host controllers.
>> > 
> I also think current OTG/Dual role framework can support your case, if you
> find there is any limitation of it which can't meet your requirement, we
> should improve it, Roger also provide an example of dual role switch with
> USB3 based on his OTG core.

Why do we need an OTG framework to support a device driver?
Is it something like a bus or class driver?

Best regards,
Lu Baolu