On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > Dear Greg, > > > On 02.08.19 18:02, Greg Kroah-Hartman wrote: > > On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > > > > On a lot of devices, like servers, you have more than one serial console, > > > and you do not always know, how they are numbered. Therefore, we start a > > > console on ttyS0 and ttyS1. > > > > > > In user space, we also would like to write to both consoles to not worry > > > about the numbering. Writing to `/dev/console` only write to the active > > > console. > > > > So the same data to multiple console devices with just one userspace > > call? Why? > > Because the cable is always connected to the port on the back side, and > sometimes the port in the front has ID 0, and the one in the back 1, and > other times vice versa. We do not want to track that, and it would be > convenient to just write to both ports. > > > > $ more /proc/consoles # I think > > > tty0 -WU (EC p ) 4:1 > > > ttyS0 -W- (E p a) 4:65 > > > ttyS1 -W- (E p a) 4:65 > > > > > > Does a device exist, or can a device be configured so you can write to > > > all (serial) consoles from user space? > > > > With one syscall, not that I know of, sorry. > > Can such a device be created with udev or so? No, a single device node can not reference multiple device nodes at the same time, sorry. That's just not how they work at all. thanks, greg k-h
