On Tue 2021-04-13 13:10:50, Samo Pogačnik wrote: > Dne 13.04.2021 (tor) ob 11:41 +0200 je Petr Mladek napisal(a): > > On Mon 2021-04-12 14:41:27, Samo Pogačnik wrote: > > > Dne 12.04.2021 (pon) ob 19:39 +0900 je Tetsuo Handa napisal(a): > > > > What is the intended usage of /dev/ttyprintk ? > > > > > > > > > > The intended use of 'ttyprintk' is to redirect console to /dev/ttyprintk > > > via the TIOCCONS ioctl. After successfull redirection, all console > > > messages get "merged" with kernel messages and as such automatically > > > processed > > > (stored/transferred) by the syslog service for example. > > > > The same can be achieved by /dev/kmsg that was created by systemd > > developers. > > > 'kmsg' and 'ttyprintk' are different types of drivers and as such rather > complementary than exclusive. The 'ttyprintk' being a tty driver allows > for a system wide automatic redirection of anything written to the > console.
I might miss something. But how can one setup ttyprintk as the system wide console? I do not see any code that would use ttyprintk in struct console. Or am I too focused on the printk/kernel-side of view? > On the other hand 'kmsg' is probably better suited for a per process > output redirection/injection of its output into kernel messages. > Maybe i am wrong, but 'systemd' could also find 'ttyprintk' usefull? /dev/kmsg allows both read and write from/to the kernel log buffer. The write callback allows to pass a certain loglevel from the user space in the format "<level>message" The read callback passes a lot of meta information in the format "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n" IMHO, /dev/kmsg provides a super set of functionality over /dev/ttyprintk. But I am not familiar with the tty layer and all its use-cases. To make it clear. I do not resist on removing ttyprintk by any means. It was just an idea. I am not even sure if it is possible to obsolete tty drivers. Best Regards, Petr
