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

[Florian Weimer]

* 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.

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

Thanks,
Florian