...

 1: static struct kobj_type ktype_block = {
 2:   .release = disk_release,
 3:   .sysfs_ops = &disk_sysfs_ops,
 4:   .default_attrs = default_attrs,
 5: };

...

 6: static struct kset_hotplug_ops block_hotplug_ops = {
 7:   .filter = block_hotplug_filter,
 8:   .hotplug = block_hotplug,
 9: };

/* declare block subsys */
10: static decl_subsys(block, &ktype_block, &block_hotplug_ops);