Simon Ser wrote: > > > Would it be possible to set the PATH connector property based on the > > > USB port used by gud? > > > > Sadly not really easily. > > > > The physical topology underneath each host controller is stable but > > bus numbers (usb1, usb2 etc.) are not. > > Oh, that's news to me. So if I unplug and replug a USB device, the bus > number and bus device number might change? The bus number is stable as long as the bus (host controller) exists. > Or does this happen after a power-cycle? Or is this hardware-specific? Consider a host controller on a plug-in card, like ExpressCard (usb1) and perhaps Thunderbolt (usb2) for a more modern example. The bus on each new host controller gets the next available bus number. Plug ExpressCard before Thunderbolt to get the order above. Unplug both (usb1+usb2 disappear) then plug Thunderbolt back in before ExpressCard; now Thunderbolt is usb1 and ExpressCard usb2. > > For onboard host controllers it could be possible to anchor to a > > PCI or platform bus device. > > But the PCI bus device isn't enough I think? If I have a onboard host > controller with 2 physical USB ports, the PCI bus device isn't enough > to tell these 2 physical ports apart? *Only* the PCI bus device is not enough, but it could serve as a unique anchor and some host controller-specific information (e.g. root port number) can be added to that. > > How about using e.g. the serial number of the gud USB device instead > > of host topology, or maybe some other information from the panel > > behind it? > > The PATH property is really about the port path, not the sink. IOW, if > I have two USB displays, one USB port, and switch between the two > displays on this one port, the PATH property isn't supposed to change. Hmm. What is "port path" supposed to mean across a hot-pluggable bus? Should PATH refer to the one ExpressCard host controller if it moves between slots (assuming a computer with two slots) or should it rather refer to "the upper USB port on the right hand side ExpressCard" so I can insert another brand host controller in that slot without PATH changing? //Peter
