Re: RFC: Serial port DTR/RTS - O_<something>

[Ned Ulbricht]

On 11/14/25 10:53, H. Peter Anvin wrote:
> On November 14, 2025 10:49:09 AM PST, "Maciej W. Rozycki" <macro@xxxxxxxxxxx> 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 [snip]

Hi all,

Resurrecting a (private email) discussion from a few years back now, my
personal preferences are:
(1) O_KEEP
(2) O_TTY_KEEP
(3) O_TTY_NOINIT.

(Of course, naming an open() flag has got to be a paradigmatic
invitation for bike-shedding...)

It's worth pointing out, though, that even though O_TTY_INIT doesn't
generally appear in linux headers, that particular flag is documented in
POSIX to have at least incompatible --perhaps even strictly opposite--
behavior compared with this new proposed flag.

See The Open Group Base Specifications Issue 8 (IEEE Std 1003.1-2024):

| 11.1.1 Opening a Terminal Device File
|
| 3. ... The terminal parameters can be set to values that ensure the
| terminal behaves in a conforming manner by means of the O_TTY_INIT
| open flag....

https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap11.html

| open, openat — open file
|
| O_TTY_INIT

https://pubs.opengroup.org/onlinepubs/9799919799/

That's what motivates my first-glance preference to name this new flag,
which will have approximately opposite behavior, as O_TTY_NOINIT.

But as a generic abstraction, I more prefer O_KEEP.

Ned