From e8c63956a5a8d0c40ac2194c545edccb727cff12 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Wed, 16 May 2018 13:55:12 +0200
Subject: [PATCH] sd-id128: return -ENOMEDIUM on null id

We currently return -ENOMEDIUM when /etc/machine-id is empty, and -EINVAL when
it is all zeros. But -EINVAL is also used for invalid args. The distinction
between empty and all-zero is not very important, let's use the same return
code.

Also document -ENOENT and -ENOMEDIUM since they can be a bit surprising.
---
 man/sd_id128_get_machine.xml       | 8 +++++---
 src/libelogind/sd-id128/sd-id128.c | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/man/sd_id128_get_machine.xml b/man/sd_id128_get_machine.xml
index 2694c186b..f3e151760 100644
--- a/man/sd_id128_get_machine.xml
+++ b/man/sd_id128_get_machine.xml
@@ -116,9 +116,11 @@
   <refsect1>
     <title>Return Value</title>
 
-    <para>The two calls return 0 on success (in which case
-    <parameter>ret</parameter> is filled in), or a negative
-    errno-style error code.</para>
+    <para>Those calls return 0 on success (in which case <parameter>ret</parameter> is filled in),
+    or a negative errno-style error code. In particular, <function>sd_id128_get_machine()</function>
+    and <function>sd_id128_get_machine_app_specific()</function> return <constant>-ENOENT</constant>
+    if <filename>/etc/machine-id</filename> is missing, and <constant>-ENOMEDIUM</constant> if is
+    empty or all zeros.</para>
   </refsect1>
 
   <refsect1>
diff --git a/src/libelogind/sd-id128/sd-id128.c b/src/libelogind/sd-id128/sd-id128.c
index af2ff8353..80548fdfc 100644
--- a/src/libelogind/sd-id128/sd-id128.c
+++ b/src/libelogind/sd-id128/sd-id128.c
@@ -98,7 +98,7 @@ _public_ int sd_id128_get_machine(sd_id128_t *ret) {
                         return r;
 
                 if (sd_id128_is_null(saved_machine_id))
-                        return -EINVAL;
+                        return -ENOMEDIUM;
         }
 
         *ret = saved_machine_id;
-- 
2.30.2