On Tue, Jun 01, 2021 at 02:39:41AM +0000, xuyang2018.jy@xxxxxxxxxxx wrote: > HI All > > I append "console=ttyS0,115200n8r" to my kernel command line and reboot > my system. > > # cat /proc/tty/driver/serial > serinfo:1.0 driver revision: > 0: uart:16550A port:000003F8 irq:4 tx:0 rx:0 RTS|DTR > 1: uart:unknown port:000002F8 irq:3 > 2: uart:unknown port:000003E8 irq:4 > 3: uart:unknown port:000002E8 irq:3 > > then I echo 1 > /dev/ttyS0, but it hangs.(If I don't use r, it works well.) 'echo' is horrible at testing serial port communication. Why not use a real serial terminal program that knows how to set the line settings? > Does it need my console connected with other machine? Something needs to be on the other end of that serial connection for this to work properly, right? > Also, many services become timeout when I use systemctl > restart/status/stop(tx,rx data doesn't increase). > > I just want to check whether it is a usage problem(my system environmet > is centos8). My machine is physical machine and virtual machine doesn't > have this problem(it has RTS|CTS|DTR|DSR|CD flag). Why do you want to use "r" here? What problem are you trying to solve? thanks, greg k-h
