Re: [PATCH] tty: Add NULL TTY driver

[Vincent Whitchurch <vincent.whitchurch@axis.com>]

On Fri, Apr 05, 2019 at 02:32:41PM +0200, Enrico Weigelt, metux IT consult wrote:
> On 05.04.19 11:00, Vincent Whitchurch wrote:
> > On Fri, Apr 05, 2019 at 10:39:43AM +0200, Enrico Weigelt, metux IT consult wrote:
> >> On 03.04.19 16:11, Vincent Whitchurch wrote:
> >>
> >>> Especially on embedded systems, it would be convenient to have a simple
> >>> way to disable the console (both for kernel and userspace) on a system
> >>> which normally uses it, to free up the UART for other things.
> >>
> >> Just symlinking to /dev/null does not work ?
> > 
> > No, /dev/null does not support the TTY ioctls.
> 
> hmm, wo (which programs) do you need, that really need them ?

I think it was systemd's debug-shell which complained about the ioctls.

> >> OTOH, if you're introducing a dummy console, wouldn't a ringbuffer that,
> >> can be read out later, a better option ?
> > 
> > There is already a ttyprintk driver in mainline to send these messages
> > to the printk ring buffer if one is actually intrested in what is
> > written to the console.  There's no option to enable it via console= in
> > mainline but I have a patch for that too.
> 
> Great. IMHO, that would be the better way.

Like Krzysztof explained, sometimes you just want to discard these
messages.