linux-kernel - Re: [PATCH] Documentation: sysrq: Remove contradicting sentence on extra /proc/sysrq-trigger characters

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Message-ID: <87wm4xbkim.fsf@trenco.lwn.net>
Date: Tue, 14 Oct 2025 08:55:29 -0600
From: Jonathan Corbet <corbet@....net>
To: Bagas Sanjaya <bagasdotme@...il.com>, Linux Kernel Mailing List
 <linux-kernel@...r.kernel.org>, Linux Documentation
 <linux-doc@...r.kernel.org>, Linux Serial <linux-serial@...r.kernel.org>
Cc: Cengiz Can <cengiz@...nel.wtf>, Bagas Sanjaya <bagasdotme@...il.com>,
 Tomas Mudrunka <tomas.mudrunka@...il.com>, Jiri Slaby
 <jirislaby@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Anselm Schüler <mail@...elmschueler.com>
Subject: Re: [PATCH] Documentation: sysrq: Remove contradicting sentence on
 extra /proc/sysrq-trigger characters

Bagas Sanjaya <bagasdotme@...il.com> writes:

> /proc/sysrq-trigger documentation states that only first character is
> processed and the rest is ignored, yet it is not recommended to write
> any extra characters to it. The latter statement is contradictive as
> these characters are also ignored as implied by preceding sentence.
>
> Remove it.
>
> Link: https://lore.kernel.org/lkml/7ca05672-dc20-413f-a923-f77ce0a9d307@anselmschueler.com/
> Signed-off-by: Bagas Sanjaya <bagasdotme@...il.com>
> ---
>  Documentation/admin-guide/sysrq.rst | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst
> index 9c7aa817adc72d..63ff415ce85d66 100644
> --- a/Documentation/admin-guide/sysrq.rst
> +++ b/Documentation/admin-guide/sysrq.rst
> @@ -77,9 +77,7 @@ On other
>  On all
>  	Write a single character to /proc/sysrq-trigger.
>  	Only the first character is processed, the rest of the string is
> -	ignored. However, it is not recommended to write any extra characters
> -	as the behavior is undefined and might change in the future versions.
> -	E.g.::
> +	ignored. E.g.::

I'm not sure this is right - there is a warning here that additional
characters may acquire a meaning in the future, so one should not
develop the habit of writing them now.  After all these years, I think
the chances of fundamental sysrq changes are pretty small, but I still
don't see why we would take the warning out?

jon