man/io_uring_enter.2: further clarify what cqe->res holds
Hopefully no one gets confused by this anymore - or, deity forbid,
throw tantrums over it.
@@ -944,13 +944,22 @@ They are described in section
.B CQE ERRORS.
.PP
For read and write opcodes, the
-return values match errno values documented in the
+return values match
+.I errno
+values documented in the
.BR preadv2 (2)
and
.BR pwritev2 (2)
-man pages.
-Return codes for the io_uring-specific opcodes are documented in the
-description of the opcodes above.
+man pages, with
+.I
+res
+holding the equivalent of
+.I -errno
+for error cases, or the transferred number of bytes in case the operation
+is succesful. Hence both error and success return can be found in that
+field in the CQE. For other request types, the return values are documented
+in the matching man page for that type, or in the opcodes section above for
+io_uring-specific opcodes.
.PP
.SH RETURN VALUE
.BR io_uring_enter ()
