Re: tty: add 'active' sysfs attribute to tty0 and console device

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> How can I detect the major and minor of the primary console device
> of /dev/console without controlling tty?  Even if my old blogd

In the general case you can't - because a console may not have a tty.
Quite a few don't. For the cases where one has a device I can't see a
clean way to do it as an fstat on the console device will give you the
console major/mninor and some code depends upon that.

The iniability to get it is clearly a flaw and you need the sysfs link or
a sysfs list of consoles (again remembering many of them won't have a tty
bound).

> and the bootlogd(8) of SysInitV using TIOCCONS are outdated by SystemD
> the question before doing the TIOCCONS is which is the primary console
> device to e.g. create the device node in initrd or for bootlogd(8)
> to write a copy of the console messages back to the original
> primary console (and the other console devices).

For init it is /dev/console as opened at boot time and passed to the
initial user init task but with no nice way to work back to a device node.

Incidentally the primary console (as in printk) can be accessed as a tty
via the ttyprintk driver which got added recently because embedded people
wanted to use the printk interface as a (write only) tty console as well.