From: John Feeney <jfeeney@redhat.com>
Date: Mon, 17 Dec 2007 15:54:15 -0500
Subject: [acpi] docking/undocking: error handling in init
Message-id: 4766E1F7.8010107@redhat.com
O-Subject: RHEL-5.2 PATCH 3/5 Docking/undocking support
Bugzilla: 252214

bz252214 FEAT: RHEL 5.2 hot dock / undock support for mobile
w/docking station
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=252214

Problem:
  ACPI: dock: Fix symbol conflict between acpiphp and dock

Solution:
  Fix bug which will cause acpiphp to not be able to load when dock.ko
  cannot load.

Upstream Status:
commit: 2548c06b72396e28abdb5dd572ab589c3c22f4b9

Testing:
The patches in this series were successfully tested by me on
a T60p, Dell Converse, and Dell Fila mobiles.

As always, acks would be appreciated.

diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
index 2630f06..73a6721 100644
--- a/drivers/acpi/dock.c
+++ b/drivers/acpi/dock.c
@@ -444,6 +444,9 @@ static int dock_in_progress(struct dock_station *ds)
  */
 int register_dock_notifier(struct notifier_block *nb)
 {
+	if (!dock_station)
+		return -ENODEV;
+
 	return atomic_notifier_chain_register(&dock_notifier_list, nb);
 }
 
@@ -455,6 +458,9 @@ EXPORT_SYMBOL_GPL(register_dock_notifier);
  */
 void unregister_dock_notifier(struct notifier_block *nb)
 {
+	if (!dock_station)
+		return;
+
 	atomic_notifier_chain_unregister(&dock_notifier_list, nb);
 }
 
@@ -842,7 +848,7 @@ static int __init dock_init(void)
 			    ACPI_UINT32_MAX, find_dock, &num, NULL);
 
 	if (!num)
-		return -ENODEV;
+		printk(KERN_INFO "No dock devices found.\n");
 
 	return 0;
 }