linux-kernel - Re: [PATCH 0/7] TTY Keyboard Status Request

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Message-ID: <20190609174139.GA11944@xo-6d-61-c0.localdomain>
Date:   Sun, 9 Jun 2019 19:41:39 +0200
From:   Pavel Machek <pavel@....cz>
To:     Arseny Maslennikov <ar@...msu.ru>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        "Vladimir D . Seleznev" <vseleznv@...linux.org>
Subject: Re: [PATCH 0/7] TTY Keyboard Status Request

Hi!

> This patch series introduces TTY keyboard status request, a feature of
> the n_tty line discipline that reserves a character in struct termios
> (^T by default) and reacts to it by printing a short informational line
> to the terminal and sending a Unix signal to the tty's foreground
> process group. The processes may, in response to the signal, output a
> textual description of what they're doing.
> 
> The feature has been present in a similar form at least in
> Free/Open/NetBSD; it would be nice to have something like this in Linux
> as well. There is an LKML thread[1] where users have previously
> expressed the rationale for this.
> 
> The current implementation does not break existing kernel API in any
> way, since, fortunately, all the architectures supported by the kernel
> happen to have at least 1 free byte in the termios control character
> array.

I like the idea... I was often wondering "how long will this dd take". (And in
case of dd, SIGUSR1 does the job).

I assume this will off by default, so that applications using ^T today will not
get surprise signals?
									Pavel