root@om:~# smartctl -a /dev/mmcblk0
smartctl 6.5 2016-01-24 r4214 [x86_64-linux-4.4.0-63-generic] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

/dev/mmcblk0: Unable to detect device type
Please specify device type with the -d option.

Use smartctl -h to get a usage summary

-d TYPE, --device=TYPE
 Specify device type to one of: ata, scsi, sat[,auto][,N][+TYPE],
 usbcypress[,X], usbjmicron[,p][,x][,N], usbsunplus, marvell, areca,N/E,
 3ware,N, hpt,L/M/N, megaraid,N, aacraid,H,L,ID, cciss,N, auto, test