[PATCH] Driver core: add generic "subsystem" link to all devices

Like the SUBSYTEM= key we find in the environment of the uevent, this
creates a generic "subsystem" link in sysfs for every device. Userspace
usually doesn't care at all if its a "class" or a "bus" device. This
provides an unified way to determine the subsytem of a device, regardless
of the way the driver core has created it.

Signed-off-by: Kay Sievers <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

block/genhd.c

···
 #include <linux/buffer_head.h>
 #include <linux/mutex.h>
 
-static struct subsystem block_subsys;
-
+struct subsystem block_subsys;
 static DEFINE_MUTEX(block_subsys_lock);
 
 /*
···
 	.uevent		= block_uevent,
 };
 
-/* declare block_subsys. */
-static decl_subsys(block, &ktype_block, &block_uevent_ops);
-
+decl_subsys(block, &ktype_block, &block_uevent_ops);
 
 /*
  * aggregate disk stat collector.  Uses the same stats that the sysfs

drivers/base/bus.c

···
 		error = device_add_attrs(bus, dev);
 		if (!error) {
 			sysfs_create_link(&bus->devices.kobj, &dev->kobj, dev->bus_id);
+			sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "subsystem");
 			sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "bus");
 		}
 	}
···
 void bus_remove_device(struct device * dev)
 {
 	if (dev->bus) {
+		sysfs_remove_link(&dev->kobj, "subsystem");
 		sysfs_remove_link(&dev->kobj, "bus");
 		sysfs_remove_link(&dev->bus->devices.kobj, dev->bus_id);
 		device_remove_attrs(dev->bus, dev);

drivers/base/class.c

···
 		goto out2;
 
 	/* add the needed attributes to this device */
+	sysfs_create_link(&class_dev->kobj, &parent_class->subsys.kset.kobj, "subsystem");
 	class_dev->uevent_attr.attr.name = "uevent";
 	class_dev->uevent_attr.attr.mode = S_IWUSR;
 	class_dev->uevent_attr.attr.owner = parent_class->owner;
···
 		sysfs_remove_link(&class_dev->kobj, "device");
 		sysfs_remove_link(&class_dev->dev->kobj, class_name);
 	}
+	sysfs_remove_link(&class_dev->kobj, "subsystem");
 	class_device_remove_file(class_dev, &class_dev->uevent_attr);
 	if (class_dev->devt_attr)
 		class_device_remove_file(class_dev, class_dev->devt_attr);

drivers/base/core.c

···
 		dev->devt_attr = attr;
 	}
 
-	if (dev->class)
+	if (dev->class) {
+		sysfs_create_link(&dev->kobj, &dev->class->subsys.kset.kobj,
+				  "subsystem");
 		sysfs_create_link(&dev->class->subsys.kset.kobj, &dev->kobj,
 				  dev->bus_id);
+	}
 
 	if ((error = device_pm_add(dev)))
 		goto PMError;
···
 		klist_del(&dev->knode_parent);
 	if (dev->devt_attr)
 		device_remove_file(dev, dev->devt_attr);
-	if (dev->class)
+	if (dev->class) {
+		sysfs_remove_link(&dev->kobj, "subsystem");
 		sysfs_remove_link(&dev->class->subsys.kset.kobj, dev->bus_id);
+	}
 	device_remove_file(dev, &dev->uevent_attr);
 
 	/* Notify the platform of the removal, in case they

fs/partitions/check.c

···
 	p->ios[0] = p->ios[1] = 0;
 	p->sectors[0] = p->sectors[1] = 0;
 	devfs_remove("%s/part%d", disk->devfs_name, part);
+	sysfs_remove_link(&p->kobj, "subsystem");
 	if (p->holder_dir)
 		kobject_unregister(p->holder_dir);
 	kobject_uevent(&p->kobj, KOBJ_REMOVE);
···
 	kobject_add(&p->kobj);
 	if (!disk->part_uevent_suppress)
 		kobject_uevent(&p->kobj, KOBJ_ADD);
+	sysfs_create_link(&p->kobj, &block_subsys.kset.kobj, "subsystem");
 	partition_sysfs_add_subdir(p);
 	disk->part[part-1] = p;
 }
···
 			kfree(disk_name);
 		}
 	}
+	sysfs_create_link(&disk->kobj, &block_subsys.kset.kobj, "subsystem");
 }
 
 /* Not exported, helper to add_disk(). */
···
 		put_device(disk->driverfs_dev);
 		disk->driverfs_dev = NULL;
 	}
+	sysfs_remove_link(&disk->kobj, "subsystem");
 	kobject_del(&disk->kobj);
 }