[PATCH v2 1/2] man/man3/errno.3: Document EFTYPE error code

[Alejandro Colomar]

Hi Florian,

On 2026-04-27T15:29:30+0200, Florian Weimer wrote:
> * Alejandro Colomar:
> 
> > Hi Florian,
> >
> > On 2026-04-27T12:34:30+0200, Florian Weimer wrote:
> >> * Alejandro Colomar:
> >> 
> >> > [CC += libc-alpha]
> >> >
> >> > Hi Dorjoy,
> >> >
> >> > On 2026-04-26T17:14:25+0600, Dorjoy Chowdhury wrote:
> >> >> Signed-off-by: Dorjoy Chowdhury <dorjoychy111@gmail.com>
> >> >
> >> > Thanks!
> >> >
> >> > 	Reviewed-by: Alejandro Colomar <alx@kernel.org>
> >> >
> >> > I will wait until glibc adds this error code to their <errno.h> before
> >> > applying the patch.  This means either you should write and send a patch
> >> > to glibc (if so, please CC me), or you should ask them to add it
> >> > themselves (if you're not comfortable writing glibc code).
> >> 
> >> I'm not sure where this is coming from.
> >
> > Here's a link to the thread:
> > <https://lore.kernel.org/linux-man/20260426111707.36541-1-dorjoychy111@gmail.com/T/>
> >
> >> POSIX says EFTYPE was rejected
> >> in favor of ENOTTY.
> >
> > Could you please share a link to that?
> >
> > Anyway, I guess ENOTTY would be inappropriate in this case.  Although
> > maybe a better error code could be devised; I don't know.  This is why
> > I wanted glibc involved in this discussion before this arrives to a
> > Linux release.  Thanks for the quick feedback!
> 
> It's in the Rationale for System Interfaces:
> 
> “
> [EFTYPE]
>     This error code was proposed in earlier proposals as "Inappropriate
>     operation for file type", meaning that the operation requested is
>     not appropriate for the file specified in the function call. This
>     code was proposed, although the same idea was covered by [ENOTTY],
>     because the connotations of the name would be misleading. It was
>     pointed out that the fcntl() function uses the error code [EINVAL]
>     for this notion, and hence all instances of [EFTYPE] were changed to
>     this code.
> ”
> 
> I replied on linux-fsdevel, too.

Thanks!

> 
> (It would be nice to submit patches introducing new error codes to
> linux-api with a subject mentioning the error code.)

Thanks!  I'll remember this advice for when receiving patches that add
error codes.

> 
> Thanks,
> Florian

Cheers,
Alex

-- 
<https://www.alejandro-colomar.es>
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