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

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Message-ID: <874l2mtuu6.fsf@gmail.com>
Date:   Mon, 12 Aug 2019 15:46:25 +0300
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Roger Quadros <rogerq@...com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Pawel Laszczak <pawell@...ence.com>
Cc:     "gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel\@ti.com" <jbergsagel@...com>,
        "nsekhar\@ti.com" <nsekhar@...com>, "nm\@ti.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


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?

-- 
balbi

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