kernel/reboot: Wrap legacy power-off callbacks into sys-off handlers

Wrap legacy power-off callbacks into sys-off handlers in order to
support co-existence of both legacy and new callbacks while we're
in process of upgrading legacy callbacks to the new API.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/reboot.c

@@ -463,6 +463,47 @@ int devm_register_sys_off_handler(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_register_sys_off_handler);
 
+static int legacy_pm_power_off_prepare(struct sys_off_data *data)
+{
+	if (pm_power_off_prepare)
+		pm_power_off_prepare();
+
+	return NOTIFY_DONE;
+}
+
+static int legacy_pm_power_off(struct sys_off_data *data)
+{
+	if (pm_power_off)
+		pm_power_off();
+
+	return NOTIFY_DONE;
+}
+
+/*
+ * Register sys-off handlers for legacy PM callbacks. This allows legacy
+ * PM callbacks co-exist with the new sys-off API.
+ *
+ * TODO: Remove legacy handlers once all legacy PM users will be switched
+ *       to the sys-off based APIs.
+ */
+static int __init legacy_pm_init(void)
+{
+	register_sys_off_handler(SYS_OFF_MODE_POWER_OFF_PREPARE,
+				 SYS_OFF_PRIO_DEFAULT,
+				 legacy_pm_power_off_prepare, NULL);
+
+	register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT,
+				 legacy_pm_power_off, NULL);
+
+	return 0;
+}
+core_initcall(legacy_pm_init);
+
+static void do_kernel_power_off_prepare(void)
+{
+	blocking_notifier_call_chain(&power_off_prep_handler_list, 0, NULL);
+}
+
 /**
  *	kernel_power_off - power_off the system
  *
@@ -471,8 +512,7 @@ EXPORT_SYMBOL_GPL(devm_register_sys_off_handler);
 void kernel_power_off(void)
 {
 	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
-	if (pm_power_off_prepare)
-		pm_power_off_prepare();
+	do_kernel_power_off_prepare();
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("Power down\n");