ACPI: create _SUN sysfs file

_SUN method provides the slot unique-ID in the ACPI namespace. And The value
is written in Advanced Configuration and Power Interface Specification as
follows:

"The _SUN value is required to be unique among the slots ofthe same type.
It is also recommended that this number match the slot number printed on
the physical slot whenever possible."

So if we can know the value, we can identify the physical position of the
slot in the system.

The patch creates "sun" file in sysfs for identifying physical position
of the slot.

Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-sun b/Documentation/ABI/testing/sysfs-devices-sun
new file mode 100644
index 000000000000..86be9848a77e
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-sun
@@ -0,0 +1,14 @@
+Whatt:          /sys/devices/.../sun
+Date:           October 2012
+Contact:        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
+Description:
+                The file contains a Slot-unique ID which provided by the _SUN
+                method in the ACPI namespace. The value is written in Advanced
+                Configuration and Power Interface Specification as follows:
+
+                "The _SUN value is required to be unique among the slots of
+                the same type. It is also recommended that this number match
+                the slot number printed on the physical slot whenever possible."
+
+                So reading the sysfs file, we can identify a physical position
+                of the slot in the system.