zdev: Integrate firmware auto-configuration with dracut

Add a dracut hook that applies firmware-provided I/O configuration data
as auto-configuration during boot. This way, all I/O devices configured
by DPM are automatically brought online without further user
interaction.

This mechanism is active by default. It can be deactivated by specifying
the following parameter on the kernel command line:

  rd.zdev=no-auto

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdev/dracut/95zdev/parse-zdev.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+#
+# Copyright IBM Corp. 2017
+#
+# s390-tools is free software; you can redistribute it and/or modify
+# it under the terms of the MIT license. See LICENSE for details.
+#
+# 95zdev/parse-zdev.sh
+#   Parse the kernel command line for rd.zdev kernel parameters. These
+#   parameters are evaluated and used to configure z Systems specific devices.
+#
+# Format:
+#   rd.zdev=no-auto
+#
+#     where
+#
+#   no-auto:       Indicates that firmware-provided I/O configuration data
+#                  should not be applied.
+#
+
+zdev_fw_file="/sys/firmware/sclp_sd/config/data"
+zdev_base_args="--force --yes --no-root-update --no-settle --auto-conf --quiet"
+
+if [ -e "$zdev_fw_file" ] ; then
+    zdev_auto=1
+else
+    zdev_auto=0
+fi
+
+for zdev_arg in $(getargs rd.zdev); do
+    if [ "$zdev_arg" = "no-auto" ] ; then
+        zdev_auto=0
+    fi
+done
+
+if [ $zdev_auto -eq 1 ] ; then
+    chzdev --import "$zdev_fw_file" $zdev_base_args
+fi