linux-kernel - Re: [PATCH v10 5/6] usb:cdns3 Add Cadence USB3 DRD Driver

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Date:   Mon, 12 Aug 2019 16:04:52 +0300
From:   Roger Quadros <rogerq@...com>
To:     Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Pawel Laszczak <pawell@...ence.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel@...com" <jbergsagel@...com>,
        "nsekhar@...com" <nsekhar@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Jayshri Dajiram Pawar <jpawar@...ence.com>,
        Rahul Kumar <kurahul@...ence.com>,
        Anil Joy Varughese <aniljoy@...ence.com>
Subject: Re: [PATCH v10 5/6] usb:cdns3 Add Cadence USB3 DRD Driver



On 12/08/2019 15:46, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
>>> The sysfs file we expose from the class for the role switches is
>>> primarily meant for supporting proprietary protocols that require us
>>> to basically override the connector USB data role. The default role
>>> should always be selected in the drivers.
>>
>> OK. Let's take this example
>> - Port is dual-role port micro AB.
>> - microAB to type-A adapter is connected which pulls ID low. port transitions
>> to "host" role by the controller driver.
>> - proprietary protocol want to switch role to device role so writes "device" to
>> mode switch sysfs. port transitions to "device" role.
>>
>> Now, how does controller driver know to fall back to HW based role switching?
> 
> Use a 'disconnect' or 'suspend' event to go reset it? But that should,
> probably, be done at kernel space, no?
> 

Yes that could be one option.
So after a disconnect, sysfs role should reflect actual hardware role. correct?

cheers,
-roger
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