On Mon, Nov 23, 2020 at 1:00 AM Martin Schiller <ms@xxxxxxxxxx> wrote: > > AFAIK the carrier can't be up before the device is up. Therefore, there > will be a NETDEV_CHANGE event after the NETDEV_UP event. > > This is what I can see in my tests (with the HDLC interface). > > Is the behaviour different for e.g. lapbether? Some drivers don't support carrier status and will never change it. Their carrier status will always be UP. There will not be a NETDEV_CHANGE event. lapbether doesn't change carrier status. I also have my own virtual HDLC WAN driver (for testing) which also doesn't change carrier status. I just tested with lapbether. When I bring up the interface, there will only be NETDEV_PRE_UP and then NETDEV_UP. There will not be NETDEV_CHANGE. The carrier status is alway UP. I haven't tested whether a device can receive NETDEV_CHANGE when it is down. It's possible for a device driver to call netif_carrier_on when the interface is down. Do you know what will happen if a device driver calls netif_carrier_on when the interface is down?
