On Fri, 21 Feb 2014, Dan Williams wrote: > ACPI identifies peer ports by setting their 'group_token' and > 'group_position' _PLD data to the same value. If a platform has tier > mismatch [1] , ACPI can override the default (USB3 defined) peer port > association for internal hubs. External hubs follow the default peer > association scheme. > > Location data is cached as an opaque cookie in usb_port_location data. > > Note that we only consider the group_token and group_position attributes > from the _PLD data as ACPI specifies that group_token is a unique > identifier. > > The bulk of the implementation is recursively fixing up peer > associations once we detect tier mismatch. Due to the way acpi data is > associated to a usb_port device (via a callback triggered by Is the callback _triggered_ (i.e., asynchronously) by device_register, or is it simply _invoked_ (synchronously) by device_register? > device_register()) we do not discover tier mismatch until after the port > has been registered. I've been thinking about this. Maybe it isn't a problem, because now you don't set up the peer matching until after the port has been registered. All you have to do is allow the ACPI data to prevent a default match if the location data values don't agree. That would simplify this patch an awful lot. Alan Stern -- 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
