aoe: make aoe_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the aoe_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: Justin Sanders <justin@coraid.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.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/20230620180129.645646-6-gregkh@linuxfoundation.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: ivanorlov2206

drivers/block/aoe/aoechr.c

@@ -49,7 +49,7 @@ static int emsgs_head_idx, emsgs_tail_idx;
 static struct completion emsgs_comp;
 static spinlock_t emsgs_lock;
 static int nblocked_emsgs_readers;
-static struct class *aoe_class;
+
 static struct aoe_chardev chardevs[] = {
 	{ MINOR_ERR, "err" },
 	{ MINOR_DISCOVER, "discover" },
@@ -58,6 +58,16 @@ static struct aoe_chardev chardevs[] = {
 	{ MINOR_FLUSH, "flush" },
 };
 
+static char *aoe_devnode(const struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "etherd/%s", dev_name(dev));
+}
+
+static const struct class aoe_class = {
+	.name = "aoe",
+	.devnode = aoe_devnode,
+};
+
 static int
 discover(void)
 {
@@ -273,11 +283,6 @@ static const struct file_operations aoe_fops = {
 	.llseek = noop_llseek,
 };
 
-static char *aoe_devnode(const struct device *dev, umode_t *mode)
-{
-	return kasprintf(GFP_KERNEL, "etherd/%s", dev_name(dev));
-}
-
 int __init
 aoechr_init(void)
 {
@@ -290,15 +295,14 @@ aoechr_init(void)
 	}
 	init_completion(&emsgs_comp);
 	spin_lock_init(&emsgs_lock);
-	aoe_class = class_create("aoe");
-	if (IS_ERR(aoe_class)) {
+	n = class_register(&aoe_class);
+	if (n) {
 		unregister_chrdev(AOE_MAJOR, "aoechr");
-		return PTR_ERR(aoe_class);
+		return n;
 	}
-	aoe_class->devnode = aoe_devnode;
 
 	for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
-		device_create(aoe_class, NULL,
+		device_create(&aoe_class, NULL,
 			      MKDEV(AOE_MAJOR, chardevs[i].minor), NULL,
 			      chardevs[i].name);
 
@@ -311,8 +315,8 @@ aoechr_exit(void)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
-		device_destroy(aoe_class, MKDEV(AOE_MAJOR, chardevs[i].minor));
-	class_destroy(aoe_class);
+		device_destroy(&aoe_class, MKDEV(AOE_MAJOR, chardevs[i].minor));
+	class_unregister(&aoe_class);
 	unregister_chrdev(AOE_MAJOR, "aoechr");
 }