Hi Peter, On Mon, Mar 06, 2017 at 09:15:51AM +0800, Peter Chen wrote: > > > 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. > > > > > > Eg, if "data_role" has changed, the udev can echo "data_role" to > > > /sys/class/usb-dual-role/role > > > > No. If the partner executes successfully for example DR_Swap message, > > the kernel has to take care everything that is needed for the role to > > be what ever was negotiated on its own. User space can't be involved > > with that. > > > > Would you give me an example how kernel handle this? How type-C event > triggers role switch? On our boards, the firmware or EC (or ACPI) configures the hardware as needed and also notifies the components using ACPI if needed. It's often not even possible to directly configure the components/hardware for a particular role. I'm not commenting on Roger's dual role patch series, but I don't really think it should be mixed with Type-C. USB Type-C and USB Power Delivery define their own ways of handling the roles, and they are not limited to the data role only. Things like OTG for example will, and actually can not be supported. With Type-C we will have competing state machines compared to OTG. The dual-role framework may be useful on systems that provide more traditional connectors, which possibly have the ID-pin like micro-AB, and possibly also support OTG. It can also be something that exist in parallel with the Type-C class, but there just can not be any dependencies between the two. Thanks, -- heikki -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
