backlight: Make backlight_class constant

Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the backlight_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240305-class_cleanup-backlight-v1-1-c0e15cc25be1@marliere.net
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 366bad51fb6b4eabcfb5fb2a7a7b73b0bb251e7f..a82934694d05c382f40bfad0dc485b8c94adf943 100644 (file)
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -319,8 +319,6 @@ static ssize_t scale_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(scale);
 
-static struct class *backlight_class;
-
 #ifdef CONFIG_PM_SLEEP
 static int backlight_suspend(struct device *dev)
 {
@@ -371,6 +369,12 @@ static struct attribute *bl_device_attrs[] = {
 };
 ATTRIBUTE_GROUPS(bl_device);
 
+static const struct class backlight_class = {
+       .name = "backlight",
+       .dev_groups = bl_device_groups,
+       .pm = &backlight_class_dev_pm_ops,
+};
+
 /**
  * backlight_force_update - tell the backlight subsystem that hardware state
  *   has changed
@@ -420,7 +424,7 @@ struct backlight_device *backlight_device_register(const char *name,
        mutex_init(&new_bd->update_lock);
        mutex_init(&new_bd->ops_lock);
 
-       new_bd->dev.class = backlight_class;
+       new_bd->dev.class = &backlight_class;
        new_bd->dev.parent = parent;
        new_bd->dev.release = bl_device_release;
        dev_set_name(&new_bd->dev, "%s", name);
@@ -512,7 +516,7 @@ struct backlight_device *backlight_device_get_by_name(const char *name)
 {
        struct device *dev;
 
-       dev = class_find_device_by_name(backlight_class, name);
+       dev = class_find_device_by_name(&backlight_class, name);
 
        return dev ? to_backlight_device(dev) : NULL;
 }
@@ -680,7 +684,7 @@ struct backlight_device *of_find_backlight_by_node(struct device_node *node)
 {
        struct device *dev;
 
-       dev = class_find_device(backlight_class, NULL, node, of_parent_match);
+       dev = class_find_device(&backlight_class, NULL, node, of_parent_match);
 
        return dev ? to_backlight_device(dev) : NULL;
 }
@@ -748,20 +752,19 @@ EXPORT_SYMBOL(devm_of_find_backlight);
 
 static void __exit backlight_class_exit(void)
 {
-       class_destroy(backlight_class);
+       class_unregister(&backlight_class);
 }
 
 static int __init backlight_class_init(void)
 {
-       backlight_class = class_create("backlight");
-       if (IS_ERR(backlight_class)) {
-               pr_warn("Unable to create backlight class; errno = %ld\n",
-                       PTR_ERR(backlight_class));
-               return PTR_ERR(backlight_class);
+       int ret;
+
+       ret = class_register(&backlight_class);
+       if (ret) {
+               pr_warn("Unable to create backlight class; errno = %d\n", ret);
+               return ret;
        }
 
-       backlight_class->dev_groups = bl_device_groups;
-       backlight_class->pm = &backlight_class_dev_pm_ops;
        INIT_LIST_HEAD(&backlight_dev_list);
        mutex_init(&backlight_dev_list_mutex);
        BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);