hwmon: (via-cputemp) Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke the
callbacks on the already online CPUs. When the hotplug state is
unregistered the cleanup function is called for each cpu. So both cpu loops
in init() and exit() are not longer required.

Cc: Jean Delvare <jdelvare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-hwmon@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/via-cputemp.c

@@ -220,7 +220,7 @@ struct pdev_entry {
 static LIST_HEAD(pdev_list);
 static DEFINE_MUTEX(pdev_list_mutex);
 
-static int via_cputemp_device_add(unsigned int cpu)
+static int via_cputemp_online(unsigned int cpu)
 {
 	int err;
 	struct platform_device *pdev;
@@ -261,7 +261,7 @@ exit:
 	return err;
 }
 
-static void via_cputemp_device_remove(unsigned int cpu)
+static int via_cputemp_down_prep(unsigned int cpu)
 {
 	struct pdev_entry *p;
 
@@ -272,33 +272,13 @@ static void via_cputemp_device_remove(unsigned int cpu)
 			list_del(&p->list);
 			mutex_unlock(&pdev_list_mutex);
 			kfree(p);
-			return;
+			return 0;
 		}
 	}
 	mutex_unlock(&pdev_list_mutex);
+	return 0;
 }
 
-static int via_cputemp_cpu_callback(struct notifier_block *nfb,
-				    unsigned long action, void *hcpu)
-{
-	unsigned int cpu = (unsigned long) hcpu;
-
-	switch (action) {
-	case CPU_ONLINE:
-	case CPU_DOWN_FAILED:
-		via_cputemp_device_add(cpu);
-		break;
-	case CPU_DOWN_PREPARE:
-		via_cputemp_device_remove(cpu);
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block via_cputemp_cpu_notifier __refdata = {
-	.notifier_call = via_cputemp_cpu_callback,
-};
-
 static const struct x86_cpu_id __initconst cputemp_ids[] = {
 	{ X86_VENDOR_CENTAUR, 6, 0xa, }, /* C7 A */
 	{ X86_VENDOR_CENTAUR, 6, 0xd, }, /* C7 D */
@@ -307,9 +287,11 @@ static const struct x86_cpu_id __initconst cputemp_ids[] = {
 };
 MODULE_DEVICE_TABLE(x86cpu, cputemp_ids);
 
+static enum cpuhp_state via_temp_online;
+
 static int __init via_cputemp_init(void)
 {
-	int i, err;
+	int err;
 
 	if (!x86_match_cpu(cputemp_ids))
 		return -ENODEV;
@@ -318,44 +300,33 @@ static int __init via_cputemp_init(void)
 	if (err)
 		goto exit;
 
-	cpu_notifier_register_begin();
-	for_each_online_cpu(i)
-		via_cputemp_device_add(i);
+	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hwmon/via:online",
+				via_cputemp_online, via_cputemp_down_prep);
+	if (err < 0)
+		goto exit_driver_unreg;
+	via_temp_online = err;
 
 #ifndef CONFIG_HOTPLUG_CPU
 	if (list_empty(&pdev_list)) {
-		cpu_notifier_register_done();
 		err = -ENODEV;
-		goto exit_driver_unreg;
+		goto exit_hp_unreg;
 	}
 #endif
-
-	__register_hotcpu_notifier(&via_cputemp_cpu_notifier);
-	cpu_notifier_register_done();
 	return 0;
 
 #ifndef CONFIG_HOTPLUG_CPU
+exit_hp_unreg:
+	cpuhp_remove_state_nocalls(via_temp_online);
+#endif
 exit_driver_unreg:
 	platform_driver_unregister(&via_cputemp_driver);
-#endif
 exit:
 	return err;
 }
 
 static void __exit via_cputemp_exit(void)
 {
-	struct pdev_entry *p, *n;
-
-	cpu_notifier_register_begin();
-	__unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
-	mutex_lock(&pdev_list_mutex);
-	list_for_each_entry_safe(p, n, &pdev_list, list) {
-		platform_device_unregister(p->pdev);
-		list_del(&p->list);
-		kfree(p);
-	}
-	mutex_unlock(&pdev_list_mutex);
-	cpu_notifier_register_done();
+	cpuhp_remove_state(via_temp_online);
 	platform_driver_unregister(&via_cputemp_driver);
 }