sound: make all 'class' structures const

Now that the driver core allows for struct class to be in read-only
memory, making all 'class' structures to be declared at build time
placing them into read-only memory, instead of having to be dynamically
allocated at load time.

Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Ivan Orlov <ivan.orlov0322@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Thierry Reding <treding@nvidia.com>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: alsa-devel@alsa-project.org
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230620175633.641141-2-gregkh@linuxfoundation.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: ivanorlov2206

include/sound/core.h

@@ -232,7 +232,7 @@ static inline struct device *snd_card_get_device_link(struct snd_card *card)
 
 extern int snd_major;
 extern int snd_ecards_limit;
-extern struct class *sound_class;
+extern const struct class sound_class;
 #ifdef CONFIG_SND_DEBUG
 extern struct dentry *sound_debugfs_root;
 #endif

sound/core/control_led.c

@@ -737,7 +737,7 @@ static int __init snd_ctl_led_init(void)
 	unsigned int group;
 
 	device_initialize(&snd_ctl_led_dev);
-	snd_ctl_led_dev.class = sound_class;
+	snd_ctl_led_dev.class = &sound_class;
 	snd_ctl_led_dev.release = snd_ctl_led_dev_release;
 	dev_set_name(&snd_ctl_led_dev, "ctl-led");
 	if (device_add(&snd_ctl_led_dev)) {

sound/core/init.c

@@ -129,7 +129,7 @@ void snd_device_initialize(struct device *dev, struct snd_card *card)
 	device_initialize(dev);
 	if (card)
 		dev->parent = &card->card_dev;
-	dev->class = sound_class;
+	dev->class = &sound_class;
 	dev->release = default_release;
 }
 EXPORT_SYMBOL_GPL(snd_device_initialize);
@@ -331,7 +331,7 @@ static int snd_card_init(struct snd_card *card, struct device *parent,
 
 	device_initialize(&card->card_dev);
 	card->card_dev.parent = parent;
-	card->card_dev.class = sound_class;
+	card->card_dev.class = &sound_class;
 	card->card_dev.release = release_card_device;
 	card->card_dev.groups = card->dev_groups;
 	card->dev_groups[0] = &card_dev_attr_group;

sound/sound_core.c

@@ -23,9 +23,6 @@ static inline int init_oss_soundcore(void)	{ return 0; }
 static inline void cleanup_oss_soundcore(void)	{ }
 #endif
 
-struct class *sound_class;
-EXPORT_SYMBOL(sound_class);
-
 MODULE_DESCRIPTION("Core sound module");
 MODULE_AUTHOR("Alan Cox");
 MODULE_LICENSE("GPL");
@@ -37,6 +34,12 @@ static char *sound_devnode(const struct device *dev, umode_t *mode)
 	return kasprintf(GFP_KERNEL, "snd/%s", dev_name(dev));
 }
 
+const struct class sound_class = {
+	.name = "sound",
+	.devnode = sound_devnode,
+};
+EXPORT_SYMBOL(sound_class);
+
 static int __init init_soundcore(void)
 {
 	int rc;
@@ -45,21 +48,19 @@ static int __init init_soundcore(void)
 	if (rc)
 		return rc;
 
-	sound_class = class_create("sound");
-	if (IS_ERR(sound_class)) {
+	rc = class_register(&sound_class);
+	if (rc) {
 		cleanup_oss_soundcore();
-		return PTR_ERR(sound_class);
+		return rc;
 	}
 
-	sound_class->devnode = sound_devnode;
-
 	return 0;
 }
 
 static void __exit cleanup_soundcore(void)
 {
 	cleanup_oss_soundcore();
-	class_destroy(sound_class);
+	class_unregister(&sound_class);
 }
 
 subsys_initcall(init_soundcore);
@@ -276,7 +277,7 @@ static int sound_insert_unit(struct sound_unit **list, const struct file_operati
 		}
 	}
 
-	device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
+	device_create(&sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
 		      NULL, "%s", s->name+6);
 	return s->unit_minor;
 
@@ -302,7 +303,7 @@ static void sound_remove_unit(struct sound_unit **list, int unit)
 		if (!preclaim_oss)
 			__unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
 					    p->name);
-		device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
+		device_destroy(&sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
 		kfree(p);
 	}
 }