Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class
To: Peter Chen <hzpeterchen@gmail.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
References: <20170221142405.76299-1-heikki.krogerus@linux.intel.com>
 <20170221142405.76299-3-heikki.krogerus@linux.intel.com>
 <20170303033529.GA18650@b29397-desktop>
Cc: Greg KH <gregkh@linuxfoundation.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Oliver Neukum <oneukum@suse.com>, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, Roger Quadros <rogerq@ti.com>,
        Jun Li <jun.li@nxp.com>
From: Guenter Roeck <linux@roeck-us.net>
Message-ID: <bbd1b0eb-7059-b72d-1fe4-27d9b5f84e0b@roeck-us.net>
Date: Thu, 2 Mar 2017 20:29:07 -0800
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On 03/02/2017 07:35 PM, Peter Chen wrote:
> On Tue, Feb 21, 2017 at 05:24:04PM +0300, Heikki Krogerus wrote:
>> +/* --------------------------------------- */
>> +/* Driver callbacks to report role updates */
>> +
>> +/**
>> + * typec_set_data_role - Report data role change
>> + * @port: The USB Type-C Port where the role was changed
>> + * @role: The new data role
>> + *
>> + * This routine is used by the port drivers to report data role changes.
>> + */
>> +void typec_set_data_role(struct typec_port *port, enum typec_data_role role)
>> +{
>> +	if (port->data_role == role)
>> +		return;
>> +
>> +	port->data_role = role;
>> +	sysfs_notify(&port->dev.kobj, NULL, "data_role");
>> +	kobject_uevent(&port->dev.kobj, KOBJ_CHANGE);
>> +}
>> +EXPORT_SYMBOL_GPL(typec_set_data_role);
>> +
>
> Hi Keikki,
>
> Have you tested this interface with real dual-role controller/board?

If it helps, my primary test system is a HP Chromebook 13 G1.

> What interface you use when you receive this event to handle
> dual-role switch? I am wonder if a common dual-role class is
> needed, then we can have a common user utility.

I don't really understand "What interface you use when you receive
this event". Can you explain ?

>
> Eg, if "data_role" has changed, the udev can echo "data_role" to
> /sys/class/usb-dual-role/role
>
That sounds like a kernel event delivered to user space via udev or
sysfs notification and returned back into the kernel through a sysfs
attribute. Do I understand that correctly ?

Thanks,
Guenter

> Maybe we can enhance Roger's drd framework [1] to fulfill that.
>
> [1] https://lwn.net/Articles/682531/
>