linux-kernel - Re: RFC: Serial port DTR/RTS

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Message-ID: <B72D6F71-7C0B-4C5A-8866-25D7946E0932@zytor.com>
Date: Fri, 14 Nov 2025 10:53:49 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
CC: Greg KH <gregkh@...uxfoundation.org>, "Theodore Ts'o" <tytso@....edu>,
        Maarten Brock <Maarten.Brock@...ls.nl>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: RFC: Serial port DTR/RTS - O_<something>

On November 14, 2025 10:49:09 AM PST, "Maciej W. Rozycki" <macro@...am.me.uk> wrote:
>On Thu, 13 Nov 2025, H. Peter Anvin wrote:
>
>> > I think this is going to be the most difficult.  I don't remember why I
>> > rejected the old submission, but maybe it would have modified the
>> > existing behaviour?  A new open flag "O_DO_NOT_TOUCH_ANYTHING" might be
>> > the simplest?
>> > 
>> 
>> Okay, to I'm going to toss out a couple suggestions for naming:
>> 
>> 	O_(PRE|FOR|N|NO)?(INIT|CONFIG|START)(DEV|HW|IO)?
>> 	O_(NO?RESET|PREPARE)(DEV|HW|IO)?
>> 	O_NO?TOUCH
>> 	O_NYET ("not yet")
>> 	
>> I think my personal preference at the moment is either O_NYET or O_PRECONFIG
>> or O_NYET; although it is perhaps a bit more "use case centric" than "what
>> actual effect it has" I think it might be clearer.  A -DEV, -HW or -IO suffix
>> would seem to needlessly preclude it being used for future similar use cases
>> for files that are not device nodes.
>
> Hmm, I'm inconvinced about any of these.
>
> How about O_FDONLY, to reflect that you are after a file descriptor only 
>with no further actions at open time while avoiding the ambiguity of names 
>such as CONFIG vs NOCONFIG or speaking more broadly implying any specific 
>intent of use at all such as with CONFIG/INIT/PREPARE/RESET/whatever?
>
> I think O_FDONLY is concise, easy to spell/say/remember, and fits the 
>purpose.  Your call!
>
>  Maciej

Overlaps too much with O_PATH, and implies that communication isn't possible *after* device-dependent setup.