linux-kernel - Re: [PATCH v17 2/3] usb: USB Type-C connector class

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Date:   Fri, 3 Mar 2017 12:52:46 +0800
From:   Peter Chen <hzpeterchen@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Oliver Neukum <oneukum@...e.com>, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, Roger Quadros <rogerq@...com>,
        Jun Li <jun.li@....com>
Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class

On Thu, Mar 02, 2017 at 08:29:07PM -0800, Guenter Roeck wrote:
> 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 ?
> 

I mean "How to trigger kernel USB controller driver do role switch?"

> >
> >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 ?
> 

Yes.

-- 

Best Regards,
Peter Chen