From 576fa64abf3b8bd6f068b37905e9e35d92eef2e9 Mon Sep 17 00:00:00 2001
From: Dan Prince <dprince@redhat.com>
Date: Wed, 19 Mar 2014 16:21:43 -0400
Subject: [PATCH] serial-console: Use udev rules to startup getty

Update the systemd serial port element implementation
so that it uses udev rules. Much nicer than
hard coding ttyS0 and ttyS1.

The udev rule only adds real serial device types
(i.e. == 4). See:

  define TTY_DRIVER_TYPE_SERIAL 0x0003

from include/linux/tty_driver.h.

Change-Id: I5d7de4815fd09c01693b7da4b8949f22fee20745
---
 elements/serial-console/README.md                         | 4 ++--
 elements/serial-console/install.d/20-stty                 | 8 +++-----
 .../serial-console/install.d/serial-console-udev.rules    | 1 +
 3 files changed, 6 insertions(+), 7 deletions(-)
 create mode 100644 elements/serial-console/install.d/serial-console-udev.rules

diff --git a/elements/serial-console/README.md b/elements/serial-console/README.md
index 73ce59c9..f753b160 100644
--- a/elements/serial-console/README.md
+++ b/elements/serial-console/README.md
@@ -1,4 +1,4 @@
-Start getty on ttyS0 and/or ttyS1
+Start getty on active serial consoles.
 
 With ILO and other remote admin environments, having a serial console can be
 useful for debugging and troubleshooting.
@@ -7,4 +7,4 @@ For upstart:
   If ttyS1 exists, getty will run on that, otherwise on ttyS0.
 
 For systemd:
-  Try to start getty on both ttyS0 and ttyS1.
+  We dynamically start a getty on any active serial port via udev rules.
diff --git a/elements/serial-console/install.d/20-stty b/elements/serial-console/install.d/20-stty
index fe1e0b12..57e6312e 100755
--- a/elements/serial-console/install.d/20-stty
+++ b/elements/serial-console/install.d/20-stty
@@ -1,12 +1,10 @@
 #!/bin/bash
-
-home=$(dirname $0)
 set -uex
+SCRIPTDIR=$(dirname $0)
 
 DIB_INIT_SYSTEM=$(dib-init-system)
 if [ "$DIB_INIT_SYSTEM" == "upstart" ]; then
-    install -m 0644 -o root -g root $home/ttySx.conf /etc/init/ttySx.conf
+    install -m 0644 -o root -g root ${SCRIPTDIR}/ttySx.conf /etc/init/ttySx.conf
 elif [ "$DIB_INIT_SYSTEM" == "systemd" ]; then
-    ln -s /usr/lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@ttyS0.service
-    ln -s /usr/lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@ttyS1.service
+    install -D -g root -o root -m 0644 ${SCRIPTDIR}/serial-console-udev.rules /etc/udev/rules.d/99-serial-console.rules
 fi
diff --git a/elements/serial-console/install.d/serial-console-udev.rules b/elements/serial-console/install.d/serial-console-udev.rules
new file mode 100644
index 00000000..a0bd6c74
--- /dev/null
+++ b/elements/serial-console/install.d/serial-console-udev.rules
@@ -0,0 +1 @@
+SUBSYSTEM=="tty", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="getty@$name.service", ATTRS{type}=="4"