i'm using 15.09 release, 4.2.0 kernel, ubuntu 15.04 , by default btmgmt is not available in the bluez version 4.101
so i had downloaded, compiled and installed the bluez
checked out the released branch 5.37
[mgmt]# public-addr 58:fc:db:40:05:b1
Set Public Address for hci0 failed with status 0x0c (Not Supported)
Do i need to use some specific kernel version where public-addr is supported?