security_password: "XXXXXX"

/dev/sda:
 Issuing SECURITY_UNLOCK command, password="XXXXXX", user=user
SECURITY_UNLOCK: Input/output error

security_password: "password_as_typed"

/dev/sda:
 Issuing SECURITY_UNLOCK command, password="password_as_typed", user=user (in 1st case) OR master (in 2nd and 3rd case)
SECURITY_UNLOCK: Input/output error

security_password: "<password>"

/dev/sda:
Issuing SECURITY_ERASE command, password="<password>", user=user
SECURITY_ERASE: Input/output error

sudo hdparm --user-master u --security-unlock <password> /dev/sda

security_password: "<password>"

/dev/sda:
 Issuing SECURITY_UNLOCK command, password="<password>", user=user
SECURITY_UNLOCK: Input/output error

sudo hdparm --user-master m --security-unlock "" /dev/sda
sudo hdparm --user-master m --security-unlock "NULL" /dev/sda
sudo hdparm --user-master m --security-unlock NULL /dev/sda

sudo hdparm --user-master m --security-unlock "                                " /dev/sda

security_password: "whatever_pw_I_provide"

/dev/sda:
 Issuing SECURITY_UNLOCK command, password="whatever_pw_I_provide", user=master
SECURITY_UNLOCK: Input/output error