On Tue, Mar 07, 2017 at 01:36:29AM +0000, Peter Chen wrote: > >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? No (firmware programs the dual-role hw/registers), but never mind. That could be the case. > If it is correct, there is a notifier between type-C > and USB controller driver, how to define this notifier for non-ACPI platform? Once there is a platform with Type-C like that, the problem needs to be solved. However.. > >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. ..what ever the solution is, it really can't rely on user space. 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
