Hi Shivanand, sorry for the delay. I just noticed this email from you.
I'm replying to the beagleboard.org community mailing list and bcc'ing
you as others may benefit from this discussion.
My guess is that your system has u-boot overlays enabled:
https://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays
The cape manager kernel driver is incompatible with u-boot overlays so
Robert Nelson has disabled the slots file:
https://elinux.org/Beagleboard:BeagleBoneBlack_Debian#Where_did_the_slots_file_go.3F
If you have further questions, then please post the contents of your
/boot/uEnv.txt
thanks,
drew