sd-login: rework error handling

Makre sure we always return sensible errors for the various, following
the same rules, and document them in a comment in sd-login.c. Also,
update all relevant man pages accordingly.

4 files changed, 127 insertions, 1 deletions

diff --git a/man/sd_get_seats.xml b/man/sd_get_seats.xml
index 5a456a5f4..4c65db37c 100644
--- a/man/sd_get_seats.xml
+++ b/man/sd_get_seats.xml
@@ -115,6 +115,29 @@
     errno-style error code.</para>
   </refsect1>
 
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
   <refsect1>
     <title>Notes</title>
 
diff --git a/man/sd_machine_get_class.xml b/man/sd_machine_get_class.xml
index 1de911657..a874249af 100644
--- a/man/sd_machine_get_class.xml
+++ b/man/sd_machine_get_class.xml
@@ -56,7 +56,7 @@
       <funcprototype>
         <funcdef>int <function>sd_machine_get_class</function></funcdef>
         <paramdef>const char* <parameter>machine</parameter></paramdef>
-        <paramdef>char *<parameter>class</parameter></paramdef>
+        <paramdef>char **<parameter>class</parameter></paramdef>
       </funcprototype>
 
       <funcprototype>
@@ -99,6 +99,35 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified machine does not exist or is currently not running.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_machine_get_class()</function> and
diff --git a/man/sd_seat_get_active.xml b/man/sd_seat_get_active.xml
index 793bbc8c9..6dda53512 100644
--- a/man/sd_seat_get_active.xml
+++ b/man/sd_seat_get_active.xml
@@ -149,6 +149,43 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
+
+        <listitem><para>Given field is not specified for the described
+        seat.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified seat is unknown.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_seat_get_active()</function>,
diff --git a/man/sd_session_is_active.xml b/man/sd_session_is_active.xml
index 55726f96a..c522a8eda 100644
--- a/man/sd_session_is_active.xml
+++ b/man/sd_session_is_active.xml
@@ -290,6 +290,43 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified session does not exist.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
+
+        <listitem><para>Given field is not specified for the described
+        session.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_session_is_active()</function>,