On Tue, Oct 24, 2023 at 09:03:22AM +0000, Simon Ser wrote: > On Tuesday, October 24th, 2023 at 09:36, Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > > > Are DP MST port numbers guaranteed to be tied to the physical hardware > > configuration (e.g. how cables are connected) and therefore stable > > across reboots? What about stable across kernel upgrades? > > > > If I knew that, I could perhaps manufacture a stable identifier in > > userspace by replacing the parent connector ID with a stable connector > > designator. > > Hm, my assumption is that these are stable, but maybe that's also wrong? > Ville, Dmitry, do you know whether the DP MST port numbers are > guaranteed stable across reboots when retaining the exact same hardware > configuration (not the software, maybe the user upgraded the kernel)? I suspect in practice those should remain the same as long as the topology didn't change, but I don't think there's anything in the DP spec that actually guarantees that (eg. some branch device could in theory reshuffle its port numbers on a whim). But there is no stable identifier for the corresponding SST connector anyway so I don't know what you would even do with stable port numbers. -- Ville Syrjälä Intel
