man: various updates

1 files changed, 20 insertions, 1 deletions

diff --git a/man/sd-login.xml b/man/sd-login.xml
index 62ec6ffefd..9926d2b85c 100644
--- a/man/sd-login.xml
+++ b/man/sd-login.xml
@@ -75,7 +75,26 @@
                 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 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>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>,