> >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. > You mean type-C trigger an ACPI event, and this ACPI event can notify related USB controller driver doing role switch? If it is correct, there is a notifier between type-C and USB controller driver, how to define this notifier for non-ACPI platform? >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. > Yes, there are two independent things. But if the kernel doesn't have a notifier between type-C message sender (type-c class) and message receiver (like USB controller driver for role switch or other drivers for alternate mode message), we had to find some ways at userspace. Peter -- 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
