[PATCH 1/2] ACPI / PM: Use register_reboot_notifier() instead of pm_power_off_prepare

[Baolin Wang <baolin.wang@linaro.org>]

We can register one notifier through register_reboot_notifier() function to
prepare to power off the system, then we can remove the 'pm_power_off_prepare'
hook in following patch.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
Note: Please help to review carefully, since I have no platform to test
this conversion.

I saw there is another reboot notifier in this driver, I am not sure the
orders between them. I can change the priority of notifier to keep their
orders if it is necessary.
---
 drivers/acpi/sleep.c |   22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index 46cde091..b3de894 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -1229,14 +1229,24 @@ static void acpi_sleep_hibernate_setup(void)
 static inline void acpi_sleep_hibernate_setup(void) {}
 #endif /* !CONFIG_HIBERNATION */
 
-static void acpi_power_off_prepare(void)
+static int acpi_reboot_notify(struct notifier_block *this, unsigned long code,
+			      void *x)
 {
-	/* Prepare to power off the system */
-	acpi_sleep_prepare(ACPI_STATE_S5);
-	acpi_disable_all_gpes();
-	acpi_os_wait_events_complete();
+	if (code == SYSTEM_POWER_OFF) {
+		/* Prepare to power off the system */
+		acpi_sleep_prepare(ACPI_STATE_S5);
+		acpi_disable_all_gpes();
+		acpi_os_wait_events_complete();
+	}
+
+	return NOTIFY_DONE;
 }
 
+static struct notifier_block acpi_reboot_notifier = {
+	.notifier_call	= acpi_reboot_notify,
+	.priority	= 0,
+};
+
 static void acpi_power_off(void)
 {
 	/* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
@@ -1261,7 +1271,7 @@ int __init acpi_sleep_init(void)
 
 	if (acpi_sleep_state_supported(ACPI_STATE_S5)) {
 		sleep_states[ACPI_STATE_S5] = 1;
-		pm_power_off_prepare = acpi_power_off_prepare;
+		register_reboot_notifier(&acpi_reboot_notifier);
 		pm_power_off = acpi_power_off;
 	} else {
 		acpi_no_s5 = true;
-- 
1.7.9.5