[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 <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

5 files changed, 17 insertions, 7 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 5a8d3bf02f17..8d7339511e5e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -17,8 +17,7 @@
 #include <linux/buffer_head.h>
 #include <linux/mutex.h>
 
-static struct subsystem block_subsys;
-
+struct subsystem block_subsys;
 static DEFINE_MUTEX(block_subsys_lock);
 
 /*
@@ -511,9 +510,7 @@ static struct kset_uevent_ops block_uevent_ops = {
         .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
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 64ba9011d1a8..050d86d0b872 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -374,6 +374,7 @@ int bus_add_device(struct device * dev)
                 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");
                 }
         }
@@ -408,6 +409,7 @@ void bus_attach_device(struct device * dev)
 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);
diff --git a/drivers/base/class.c b/drivers/base/class.c
index 50e841a33af0..9aa127460262 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -561,6 +561,7 @@ int class_device_add(struct class_device *class_dev)
                 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;
@@ -737,6 +738,7 @@ void class_device_del(struct class_device *class_dev)
                 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);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 252cf403f891..cc8bb97427d0 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -319,9 +319,12 @@ int device_add(struct device *dev)
                 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;
@@ -422,8 +425,10 @@ void device_del(struct device * dev)
                 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
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 7ef1f094de91..8851b81e7c5a 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -329,6 +329,7 @@ void delete_partition(struct gendisk *disk, int part)
         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);
@@ -363,6 +364,7 @@ void add_partition(struct gendisk *disk, int part, sector_t start, sector_t len)
         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;
 }
@@ -398,6 +400,7 @@ static void disk_sysfs_symlinks(struct gendisk *disk)
                         kfree(disk_name);
                 }
         }
+        sysfs_create_link(&disk->kobj, &block_subsys.kset.kobj, "subsystem");
 }
 
 /* Not exported, helper to add_disk(). */
@@ -548,5 +551,6 @@ void del_gendisk(struct gendisk *disk)
                 put_device(disk->driverfs_dev);
                 disk->driverfs_dev = NULL;
         }
+        sysfs_remove_link(&disk->kobj, "subsystem");
         kobject_del(&disk->kobj);
 }