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From: "Ricardo B. Marliere" <ricardo@marliere.net>
Date: Tue, 05 Mar 2024 09:21:17 -0300
Subject: [PATCH 1/2] video: backlight: make backlight_class constant
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Message-Id: <20240305-class_cleanup-backlight-v1-1-c0e15cc25be1@marliere.net>
References: <20240305-class_cleanup-backlight-v1-0-c0e15cc25be1@marliere.net>
In-Reply-To: <20240305-class_cleanup-backlight-v1-0-c0e15cc25be1@marliere.net>
To: Lee Jones <lee@kernel.org>, 
 Daniel Thompson <daniel.thompson@linaro.org>, 
 Jingoo Han <jingoohan1@gmail.com>, Helge Deller <deller@gmx.de>
Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, 
 linux-kernel@vger.kernel.org, "Ricardo B. Marliere" <ricardo@marliere.net>, 
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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>
---
 drivers/video/backlight/backlight.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 86e1cdc8e369..d2feaebfd84a 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -317,8 +317,6 @@ 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)
 {
@@ -369,6 +367,12 @@ 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
@@ -418,7 +422,7 @@ 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);
@@ -510,7 +514,7 @@ 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;
 }
@@ -678,7 +682,7 @@ 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;
 }
@@ -746,20 +750,19 @@ 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);

-- 
2.43.0