On Wed, Feb 19, 2020 at 12:19:13PM +0100, Johan Hovold wrote: > On Wed, Feb 19, 2020 at 12:03:06PM +0100, Uwe Kleine-König wrote: > > On Wed, Feb 19, 2020 at 11:52:39AM +0100, Johan Hovold wrote: > > If I understand correctly calling tty_kopen_shared() doesn't open the > > device, just keep it referenced which prevents it to disappear. Unless I > > miss something it doesn't result in the tty's .open() being called. > > So tty_kopen_shared() is something you added. Judging from a quick look > it seems you can only attach a trigger to an already open port, but the > trigger will then keep the port open (again, consider modem control, > power). Sorry, my bad; this reference shouldn't prevent the port from being closed. The fact that you need the port to be open before you can attach a trigger does sound like a problem though (e.g. consider udev rules). Johan