In prior conversations with folks doing utilities such as lsscsi, it became
rather apparent that it is difficult to establish the relationships between
the class device and its base device. The class->device symlink is good for
one direction, but the reverse direction didn't exist. In order to go from
the device to its class device, you needed to either search all class
devices to search for a device backlink that pointed to you, or had to build
in name relationships what the subset class devices that you need to look at.
This patch adds a symlink from the base device to the class device. The name
of the symlink is "class:<classname>". I had originally considered just
<classname> for the symlink name, but it seemed to get lost in the attributes.
-- James S
Example:
# cd /sys/class/scsi_host/host0
# ls -ld device
lrwxrwxrwx 1 root root 0 Aug 13 11:11 device -> ../../../devices/platform/host0
# cd ../../../devices/platform/host0
# pwd
/sys/devices/platform/host0
# ls
class:scsi_host power target0:0:0 target0:0:1 target0:0:2 target0:0:3
# ls -ld class*
lrwxrwxrwx 1 root root 0 Aug 13 07:08 class:scsi_host ->
../../../class/scsi_host/host0
diff -upNr a/drivers/base/class.c b/drivers/base/class.c
--- a/drivers/base/class.c 2005-08-13 10:46:33.000000000 -0400
+++ b/drivers/base/class.c 2005-08-13 11:06:51.000000000 -0400
@@ -495,9 +495,13 @@ int class_device_add(struct class_device
}
class_device_add_attrs(class_dev);
- if (class_dev->dev)
+ if (class_dev->dev) {
+ char buf[40];
sysfs_create_link(&class_dev->kobj,
&class_dev->dev->kobj, "device");
+ snprintf(buf, 40, "class:%s", class_dev->class->name);
+ sysfs_create_link(&class_dev->dev->kobj, &class_dev->kobj, buf);
+ }
/* notify any interfaces this device is now here */
if (parent) {
@@ -589,8 +593,12 @@ void class_device_del(struct class_devic
up(&parent->sem);
}
- if (class_dev->dev)
+ if (class_dev->dev) {
+ char buf[40];
+ snprintf(buf, 40, "class:%s", class_dev->class->name);
+ sysfs_remove_link(&class_dev->dev->kobj, buf);
sysfs_remove_link(&class_dev->kobj, "device");
+ }
if (class_dev->devt_attr) {
class_device_remove_file(class_dev, class_dev->devt_attr);
kfree(class_dev->devt_attr);
-
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