scsi: sg: Make sg_sysfs_class constant

Since commit 43a7206b ("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 sg_sysfs_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>
Link: https://lore.kernel.org/r/20240302-class_cleanup-scsi-v1-1-b9096b990e27@marliere.netSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sg.c

@@ -1424,7 +1424,9 @@ static const struct file_operations sg_fops = {
 	.llseek = no_llseek,
 };
 
-static struct class *sg_sysfs_class;
+static const struct class sg_sysfs_class = {
+	.name = "scsi_generic"
+};
 
 static int sg_sysfs_valid = 0;
 
@@ -1526,7 +1528,7 @@ sg_add_device(struct device *cl_dev)
 	if (sg_sysfs_valid) {
 		struct device *sg_class_member;
 
-		sg_class_member = device_create(sg_sysfs_class, cl_dev->parent,
+		sg_class_member = device_create(&sg_sysfs_class, cl_dev->parent,
 						MKDEV(SCSI_GENERIC_MAJOR,
 						      sdp->index),
 						sdp, "%s", sdp->name);
@@ -1616,7 +1618,7 @@ sg_remove_device(struct device *cl_dev)
 	read_unlock_irqrestore(&sdp->sfd_lock, iflags);
 
 	sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
-	device_destroy(sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));
+	device_destroy(&sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));
 	cdev_del(sdp->cdev);
 	sdp->cdev = NULL;
 
@@ -1687,11 +1689,9 @@ init_sg(void)
 				    SG_MAX_DEVS, "sg");
 	if (rc)
 		return rc;
-        sg_sysfs_class = class_create("scsi_generic");
-        if ( IS_ERR(sg_sysfs_class) ) {
-		rc = PTR_ERR(sg_sysfs_class);
+	rc = class_register(&sg_sysfs_class);
+	if (rc)
 		goto err_out;
-        }
 	sg_sysfs_valid = 1;
 	rc = scsi_register_interface(&sg_interface);
 	if (0 == rc) {
@@ -1700,7 +1700,7 @@ init_sg(void)
 #endif				/* CONFIG_SCSI_PROC_FS */
 		return 0;
 	}
-	class_destroy(sg_sysfs_class);
+	class_unregister(&sg_sysfs_class);
 	register_sg_sysctls();
 err_out:
 	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), SG_MAX_DEVS);
@@ -1715,7 +1715,7 @@ exit_sg(void)
 	remove_proc_subtree("scsi/sg", NULL);
 #endif				/* CONFIG_SCSI_PROC_FS */
 	scsi_unregister_interface(&sg_interface);
-	class_destroy(sg_sysfs_class);
+	class_unregister(&sg_sysfs_class);
 	sg_sysfs_valid = 0;
 	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
 				 SG_MAX_DEVS);