X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=man%2Fsystemd-backlight%40.service.xml;h=21c6437efab4d277a800cd6dea607c5703ffaeb0;hb=5fae368bda9419d9d378ea32077c8fd183dd4b81;hp=f2f54728a3f872576be3ca4dadeaeb813c9b1356;hpb=38e19f93501d5a23d2176be30eea82e1be999f3d;p=elogind.git

diff --git a/man/systemd-backlight@.service.xml b/man/systemd-backlight@.service.xml
index f2f54728a..21c6437ef 100644
--- a/man/systemd-backlight@.service.xml
+++ b/man/systemd-backlight@.service.xml
@@ -56,11 +56,37 @@
 
                 <para><filename>systemd-backlight@.service</filename>
                 is a service that restores the display backlight
-                brightness at early-boot and saves it at shutdown. On
-                disk the backlight brightness is stored in
-                <filename>/var/lib/backlight/</filename>. Note that by
-                default only firmware backlight devices are
-                saved/restored.</para>
+                brightness at early boot and saves it at shutdown. On
+                disk, the backlight brightness is stored in
+                <filename>/var/lib/systemd/backlight/</filename>. During
+                loading, if udev property
+                <option>ID_BACKLIGHT_CLAMP</option> is not set to
+                false value, the brightness is clamped to a value of
+                at least 1 or 5% of maximum brightness, whichever is
+                greater. This restriction will be removed when the
+                kernel allows user space to reliably set a brightness
+                value which does not turn off the display.</para>
+        </refsect1>
+
+        <refsect1>
+                <title>Kernel Command Line</title>
+
+                <para><filename>systemd-backlight</filename> understands
+                the following kernel command line parameter:</para>
+
+                <variablelist class='kernel-commandline-options'>
+                        <varlistentry>
+                                <term><varname>systemd.restore_state=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. Defaults to
+                                <literal>1</literal>. If
+                                <literal>0</literal>, does not restore
+                                the backlight settings on boot. However,
+                                settings will still be stored on shutdown.
+                                </para></listitem>
+                        </varlistentry>
+                </variablelist>
         </refsect1>
 
         <refsect1>