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

[Guenter Roeck]

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/