docs: rebase html documentation for online and local use

[elogind.git] / man / sd-login.xml

diff --git a/man/sd-login.xml b/man/sd-login.xml
index 62ec6ffefd07e3dc6e8bfef5547233b03c6cc479..acb78ac6896f63eac701f0ac121228b3d8f90e2f 100644 (file)
--- a/man/sd-login.xml
+++ b/man/sd-login.xml
@@ -8,16 +8,16 @@
   Copyright 2010 Lennart Poettering
 
   systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
   (at your option) any later version.
 
   systemd is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  General Public License for more details.
+  Lesser General Public License for more details.
 
-  You should have received a copy of the GNU General Public License
+  You should have received a copy of the GNU Lesser General Public License
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 -->
 
@@ -75,7 +75,36 @@
                 actively make changes to the seat configuration,
                 terminate login sessions, or switch session on a seat
                 you need to utilize the D-Bus API of
-                systemd-logind.</para>
+                systemd-logind, instead.</para>
+
+                <para>These functions synchronously access data in
+                <filename>/proc</filename>,
+                <filename>/sys/fs/cgroup</filename> and
+                <filename>/run</filename>. All of these are virtual
+                file systems, hence the runtime cost of the accesses
+                is relatively cheap.</para>
+
+                <para>It is possible (and often a very good choice) to
+                mix calls to the synchronous interface of
+                <filename>sd-login.h</filename> with the asynchronous
+                D-Bus interface of systemd-logind. However, if this is
+                done you need to think a bit about possible races
+                since the stream of events from D-Bus and from
+                <filename>sd-login.h</filename> interfaces such as the
+                login monitor are asynchronous and not ordered against
+                each other.</para>
+
+                <para>If the functions return string arrays, these are
+                generally NULL terminated and need to be freed by the
+                caller with the libc
+                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                call after use, including the strings referenced
+                therein. Similar, individual strings returned need to
+                be freed, as well.</para>
+
+                <para>As a special exception, instead of an empty
+                string array NULL may be returned, which should be
+                treated equivalent to an empty string array.</para>
 
                 <para>See
                 <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,