Based on kernel version 4.3. Page generated on 2015-11-02 12:43 EST.
1 What: /sys/devices/.../sun 2 Date: October 2012 3 Contact: Yasuaki Ishimatsu <email@example.com> 4 Description: 5 The file contains a Slot-unique ID which provided by the _SUN 6 method in the ACPI namespace. The value is written in Advanced 7 Configuration and Power Interface Specification as follows: 8 9 "The _SUN value is required to be unique among the slots of 10 the same type. It is also recommended that this number match 11 the slot number printed on the physical slot whenever possible." 12 13 So reading the sysfs file, we can identify a physical position 14 of the slot in the system.