From: Peter Chen <peter.chen@nxp.com>
To: Guenter Roeck <linux@roeck-us.net>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
CC: Peter Chen <hzpeterchen@gmail.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Oliver Neukum <oneukum@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        Roger Quadros <rogerq@ti.com>, Jun Li <jun.li@nxp.com>
Subject: RE: [PATCH v17 2/3] usb: USB Type-C connector class
Thread-Topic: [PATCH v17 2/3] usb: USB Type-C connector class
Thread-Index: AQHSjE7Zns8DlLo/Z0qwb9O6z97wi6GChcqAgAC3ToCAA9itgIAAyUyAgADLioCAAH6WgIABG7iAgABSkDA=
Date: Wed, 8 Mar 2017 06:50:12 +0000
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References: <20170221142405.76299-1-heikki.krogerus@linux.intel.com>
 <20170221142405.76299-3-heikki.krogerus@linux.intel.com>
 <20170303033529.GA18650@b29397-desktop>
 <20170303143133.GB6999@kuha.fi.intel.com>
 <20170306011551.GA23305@b29397-desktop>
 <20170306131619.GD6999@kuha.fi.intel.com>
 <HE1PR04MB1450230528B5C0B88235E6E08B2F0@HE1PR04MB1450.eurprd04.prod.outlook.com>
 <20170307085753.GF6999@kuha.fi.intel.com>
 <f7184bac-e966-91cd-c10b-7f84a4d65071@roeck-us.net>
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>>> You mean type-C trigger an ACPI event, and this ACPI event can notify
>>> related USB controller driver doing role switch?
>>
>> No (firmware programs the dual-role hw/registers), but never mind.
>> That could be the case.
>>
>>> If it is correct, there is a notifier between type-C and USB
>>> controller driver, how to define this notifier for non-ACPI platform?
>>
>> Once there is a platform with Type-C like that, the problem needs to
>> be solved. However..
>>
>>>> I'm not commenting on Roger's dual role patch series, but I don't
>>>> really think it should be mixed with Type-C. USB Type-C and USB
>>>> Power Delivery define their own ways of handling the roles, and they
>>>> are not limited to the data role only. Things like OTG for example
>>>> will, and actually can not be supported. With Type-C we will have
>>>> competing state machines compared to OTG. The dual-role framework
>>>> may be useful on systems that provide more traditional connectors,
>>>> which possibly have the ID-pin like micro-AB, and possibly also
>>>> support OTG. It can also be something that exist in parallel with the Type-C
>class, but there just can not be any dependencies between the two.
>>>>
>>>
>>> Yes, there are two independent things. But if the kernel doesn't have
>>> a notifier between type-C message sender (type-c class) and message
>>> receiver (like USB controller driver for role switch or other drivers
>>> for alternate mode message), we had to find some ways at userspace.
>>
>> ..what ever the solution is, it really can't rely on user space.
>>
>
>... and, at least for our application, using extcon for the necessary notifications works
>just fine.
>

I see, that means you have a hardware signal to notify role switch.

Peter