units: add usb-gadget target

Linux can be run on a device meant to act as a USB peripheral. In order
for a machine to act as such a USB device it has to be equipped with
a UDC - USB Device Controller.

This patch adds a target reached when UDC becomes available. It can be used
for activating e.g. a service unit which composes a USB gadget with
configfs and activates it.

diff --git a/man/systemd.special.xml b/man/systemd.special.xml
index fd5639ba03e5d8b4b246c84eeeb283fab8e3a9b0..5e1f4469af0bc1c8e6d7562811ab02add727ad99 100644 (file)
--- a/man/systemd.special.xml
+++ b/man/systemd.special.xml
@@ -83,6 +83,7 @@
     <filename>time-sync.target</filename>,
     <filename>timers.target</filename>,
     <filename>umount.target</filename>,
+    <filename>usb-gadget.target</filename>,
     <!-- slices --><filename>-.slice</filename>,
     <filename>system.slice</filename>,
     <filename>user.slice</filename>,
@@ -799,6 +800,16 @@
             dynamically when audio hardware is found.</para>
           </listitem>
         </varlistentry>
+        <varlistentry>
+          <term><filename>usb-gadget.target</filename></term>
+          <listitem>
+            <para>This target is started automatically as soon as a
+            USB Device Controller becomes available at boot.</para>
+
+            <para>This may be used to pull in usb gadget
+            dynamically when UDC hardware is found.</para>
+          </listitem>
+        </varlistentry>
       </variablelist>
     </refsect2>
 

diff --git a/rules/99-systemd.rules.in b/rules/99-systemd.rules.in
index 419ca4ed87990f054f7891e76e79afff08afc9d1..f982631766b1c9d25c4687256aeffa1a588e5bb7 100644 (file)
--- a/rules/99-systemd.rules.in
+++ b/rules/99-systemd.rules.in
@@ -56,6 +56,8 @@ SUBSYSTEM=="printer", TAG+="systemd", ENV{SYSTEMD_WANTS}+="printer.target"
 SUBSYSTEM=="usb", KERNEL=="lp*", TAG+="systemd", ENV{SYSTEMD_WANTS}+="printer.target"
 SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ENV{ID_USB_INTERFACES}=="*:0701??:*", TAG+="systemd", ENV{SYSTEMD_WANTS}+="printer.target"
 
+SUBSYSTEM=="udc", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="usb-gadget.target"
+
 # Apply sysctl variables to network devices (and only to those) as they appear.
 ACTION=="add", SUBSYSTEM=="net", KERNEL!="lo", RUN+="@rootlibexecdir@/systemd-sysctl --prefix=/net/ipv4/conf/$name --prefix=/net/ipv4/neigh/$name --prefix=/net/ipv6/conf/$name --prefix=/net/ipv6/neigh/$name"
 

diff --git a/units/usb-gadget.target b/units/usb-gadget.target
new file mode 100644 (file)
index 0000000..c666683
--- /dev/null
+++ b/units/usb-gadget.target
@@ -0,0 +1,12 @@
+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  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.
+
+[Unit]
+Description=Hardware activated USB gadget
+Documentation=man:systemd.special(7)