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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=t2a47GvC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="t2a47GvC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C824AC4CEF9; Wed, 15 Oct 2025 06:18:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760509127; bh=DZF1ndhiUAR/WGmgBw5roqEhlUKaFpXC0/Hq0pMgxvA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=t2a47GvCC4giD+p4QyoA+z/aI+GrrlVChjRRbuPfvgp148Oj17vUBPEC9fofuSUA6 iGgL8tzglzkrLdJwRC19LYuGAsXyAViyPXkNnkfTUBGTSXmMtD7B8bISk6tar8plfl ayxYHWxwIqpM/yrR0056Vj0uOOiiu8Bcn74CCL3QW+AS1aGPBcH2vTRd9K/Yl7PCIT hx9zxvcEhKvW5PTs+7r1Z84bgC+z1imm1c1S5bPCgD4bnJvgQtO4TGxvqRqUP0eiQF xB/WSgMGh208yb2b43ztvaBK4fVOTana+awcFwhFib/mHBN3Anr94O5KMwPqakgMVo ogjpoAfvINBxA== Message-ID: <0cc09ea7-d4f7-4e1c-9cd0-bf310faba217@kernel.org> Date: Wed, 15 Oct 2025 08:18:44 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Documentation: sysrq: Remove contradicting sentence on extra /proc/sysrq-trigger characters To: Bagas Sanjaya , Randy Dunlap , Jonathan Corbet , Linux Kernel Mailing List , Linux Documentation , Linux Serial Cc: Cengiz Can , Tomas Mudrunka , Greg Kroah-Hartman , =?UTF-8?Q?Anselm_Sch=C3=BCler?= References: <20251008112409.33622-1-bagasdotme@gmail.com> <87wm4xbkim.fsf@trenco.lwn.net> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 15. 10. 25, 2:11, Bagas Sanjaya wrote: > On Tue, Oct 14, 2025 at 10:57:45AM -0700, Randy Dunlap wrote: >> >> >> On 10/14/25 7:55 AM, Jonathan Corbet wrote: >>> Bagas Sanjaya 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 >>>> --- >>>> 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? >> >> but the following paragraph says: >> >> Alternatively, write multiple characters prepended by underscore. >> This way, all characters will be processed. E.g.:: >> >> echo _reisub > /proc/sysrq-trigger >> >> so it is confuzing. > > I guess the whole "On all" description can be rewritten like: > > Write a single character to /proc/sysrq-trigger, e.g.:: > > ... > > If a string (multiple characters) is written instead, only the first character > is processed unless the string is prepended by an underscore, like:: > > ... Some kind of, yes. So Either: * you write no underscore and a character -- the rest is ignored and you should not write more than one. * you prepend underscore and write more of them -- all are processed. thanks, -- js suse labs