Security Manager (sm)

The commands in this section are used to manage Bluetooth security, including commands for starting and stopping encryption and commands for management of all bonding operations.

The following procedure can be used to bond with a remote device:

If MITM is required, the application needs to display or ask user to enter a passkey during the process. See events sm_passkey_display and sm_passkey_request for more information. The following procedure can be used to respond the bonding initiated by a remote device:

If MITM is required, the application needs to display or ask user to enter a passkey during the process. See events sm_passkey_display and sm_passkey_request for more information.

sm commands

sm_add_to_whitelist

This command can be used to add device to whitelist, which can be enabled with le_gap_enable_whitelisting

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x07 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x13 method Message ID
4-9 bd_addr address Address of the device added to whitelist
10 uint8 address_type Address type of the device added to whitelist

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x13 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_add_to_whitelist_rsp_t *gecko_cmd_sm_add_to_whitelist(bd_addr address, uint8 address_type);

/* Response id */
gecko_rsp_sm_add_to_whitelist_id

/* Response structure */
struct gecko_msg_sm_add_to_whitelist_rsp_t
{
  uint16 result
}

sm_bonding_confirm

This command can be used for accepting or rejecting bonding request.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0e method Message ID
4 uint8 connection Connection handle
5 uint8 confirm Accept bonding request. Values:
  • 0: Reject
  • 1: Accept bonding request

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0e method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_bonding_confirm_rsp_t *gecko_cmd_sm_bonding_confirm(uint8 connection, uint8 confirm);

/* Response id */
gecko_rsp_sm_bonding_confirm_id

/* Response structure */
struct gecko_msg_sm_bonding_confirm_rsp_t
{
  uint16 result
}

sm_configure

This command can be used to configure security requirements and I/O capabilities of the system.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x01 method Message ID
4 uint8 flags Security requirement bitmask.
Bit 0:
  • 0: Allow bonding without MITM protection
  • 1: Bonding requires MITM protection
Bit 1:
  • 0: Allow encryption without bonding
  • 1: Encryption requires bonding. Note that this setting will also enable bonding.
Bit 2:
  • 0: Allow bonding with legacy pairing
  • 1: Secure connections only
Bit 3:
  • 0: Bonding request does not need to be confirmed
  • 1: Bonding requests need to be confirmed. Received bonding requests are notified with sm_confirm_bonding events.
Bit 4 to 7: Reserved

Default value: 0x00
5 uint8 io_capabilities I/O Capabilities. See link

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x01 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_configure_rsp_t *gecko_cmd_sm_configure(uint8 flags, uint8 io_capabilities);

/* Response id */
gecko_rsp_sm_configure_id

/* Response structure */
struct gecko_msg_sm_configure_rsp_t
{
  uint16 result
}

sm_delete_bonding

This command can be used to delete specified bonding information or whitelist from Persistent Store.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x06 method Message ID
4 uint8 bonding Bonding handle

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x06 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_delete_bonding_rsp_t *gecko_cmd_sm_delete_bonding(uint8 bonding);

/* Response id */
gecko_rsp_sm_delete_bonding_id

/* Response structure */
struct gecko_msg_sm_delete_bonding_rsp_t
{
  uint16 result
}

sm_delete_bondings

This command can be used to delete all bonding information and whitelist from Persistent Store.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x00 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x07 method Message ID

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x07 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_delete_bondings_rsp_t *gecko_cmd_sm_delete_bondings();

/* Response id */
gecko_rsp_sm_delete_bondings_id

/* Response structure */
struct gecko_msg_sm_delete_bondings_rsp_t
{
  uint16 result
}

sm_enter_passkey

This command can be used to enter a passkey after receiving a passkey request event.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x05 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x08 method Message ID
4 uint8 connection Connection handle
5-8 int32 passkey Passkey. Valid range: 0-999999. Set -1 to cancel pairing.

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x08 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_enter_passkey_rsp_t *gecko_cmd_sm_enter_passkey(uint8 connection, int32 passkey);

/* Response id */
gecko_rsp_sm_enter_passkey_id

/* Response structure */
struct gecko_msg_sm_enter_passkey_rsp_t
{
  uint16 result
}

sm_increase_security

This command can be used to enhance the security of a connection to current security requirements. On an unencrypted connection, this will encrypt the connection and will also perform bonding if requested by both devices. On an encrypted connection, this will cause the connection re-encrypted.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x04 method Message ID
4 uint8 connection Connection handle

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x04 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_increase_security_rsp_t *gecko_cmd_sm_increase_security(uint8 connection);

/* Response id */
gecko_rsp_sm_increase_security_id

/* Response structure */
struct gecko_msg_sm_increase_security_rsp_t
{
  uint16 result
}

Events generated

Event Description
le_connection_parameters This event is triggered after increasing security has been completed successfully, and indicates the latest security mode of the connection.
sm_bonded This event is triggered if pairing or bonding was performed in this operation and the result is success.
sm_bonding_failed This event is triggered if pairing or bonding was performed in this operation and the result is failure.

sm_list_all_bondings

This command can be used to list all bondings stored in the bonding database. Bondings are reported by using the sm_list_bonding_entry event for each bonding and the report is ended with sm_list_all_bondings_complete event. Recommended to be used only for debugging purposes, because reading from the Persistent Store is relatively slow.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x00 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0b method Message ID

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0b method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_list_all_bondings_rsp_t *gecko_cmd_sm_list_all_bondings();

/* Response id */
gecko_rsp_sm_list_all_bondings_id

/* Response structure */
struct gecko_msg_sm_list_all_bondings_rsp_t
{
  uint16 result
}

Events generated

Event Description
sm_list_bonding_entry
sm_list_all_bondings_complete

sm_passkey_confirm

This command can be used for accepting or rejecting reported confirm value.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x09 method Message ID
4 uint8 connection Connection handle
5 uint8 confirm Accept confirm value. Values:
  • 0: Reject
  • 1: Accept confirm value

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x09 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_passkey_confirm_rsp_t *gecko_cmd_sm_passkey_confirm(uint8 connection, uint8 confirm);

/* Response id */
gecko_rsp_sm_passkey_confirm_id

/* Response structure */
struct gecko_msg_sm_passkey_confirm_rsp_t
{
  uint16 result
}

sm_set_bondable_mode

This command can be used to set whether the device should accept new bondings. By default, the device does not accept new bondings.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x00 method Message ID
4 uint8 bondable Bondable mode. Values:
  • 0: New bondings not accepted
  • 1: Bondings allowed

Default value: 0

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x00 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_set_bondable_mode_rsp_t *gecko_cmd_sm_set_bondable_mode(uint8 bondable);

/* Response id */
gecko_rsp_sm_set_bondable_mode_id

/* Response structure */
struct gecko_msg_sm_set_bondable_mode_rsp_t
{
  uint16 result
}

sm_set_debug_mode

This command can be used to set Security Manager in debug mode. In this mode the secure connections bonding uses debug keys, so that the encrypted packet can be opened by Bluetooth protocol analyzer. To disable the debug mode, you need to restart the device.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x00 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0f method Message ID

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0f method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_set_debug_mode_rsp_t *gecko_cmd_sm_set_debug_mode();

/* Response id */
gecko_rsp_sm_set_debug_mode_id

/* Response structure */
struct gecko_msg_sm_set_debug_mode_rsp_t
{
  uint16 result
}

sm_set_oob_data

This command can be used to set the OOB data (out-of-band encryption data) for legacy pairing for a device. The OOB data may be, for example, a PIN code exchanged over an alternate path like NFC. The device will not allow any other kind of bonding if OOB data is set. The OOB data cannot be set simultaneously with secure connections OOB data.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0a method Message ID
4 uint8array oob_data OOB data. To set OOB data, send a 16-byte array. To clear OOB data, send a zero-length array.

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x0a method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_set_oob_data_rsp_t *gecko_cmd_sm_set_oob_data(uint8 oob_data_len, const uint8 *oob_data_data);

/* Response id */
gecko_rsp_sm_set_oob_data_id

/* Response structure */
struct gecko_msg_sm_set_oob_data_rsp_t
{
  uint16 result
}

sm_set_passkey

This command can be used to enter a fixed passkey which will be used in the sm_passkey_display event.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x04 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x10 method Message ID
4-7 int32 passkey Passkey. Valid range: 0-999999. Set -1 to disable and start using random passkeys.

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x10 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_set_passkey_rsp_t *gecko_cmd_sm_set_passkey(int32 passkey);

/* Response id */
gecko_rsp_sm_set_passkey_id

/* Response structure */
struct gecko_msg_sm_set_passkey_rsp_t
{
  uint16 result
}

sm_set_sc_remote_oob_data

This command can be used to set OOB data and confirm values (out-of-band encryption) received from the remote device for secure connections pairing. OOB data must be enabled with sm_use_sc_oob before setting the remote device OOB data.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x12 method Message ID
4 uint8array oob_data Remote device OOB data and confirm values. To set OOB data, send a 32-byte array. First 16-bytes is the OOB data and last 16-bytes the confirm value. To clear OOB data, send a zero-length array.

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x12 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_set_sc_remote_oob_data_rsp_t *gecko_cmd_sm_set_sc_remote_oob_data(uint8 oob_data_len, const uint8 *oob_data_data);

/* Response id */
gecko_rsp_sm_set_sc_remote_oob_data_id

/* Response structure */
struct gecko_msg_sm_set_sc_remote_oob_data_rsp_t
{
  uint16 result
}

sm_store_bonding_configuration

This command can be used to set maximum allowed bonding count and bonding policy. The actual maximum number of bondings that can be supported depends on how much user data is stored in the NVM and the NVM size. The default value is 14.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x02 method Message ID
4 uint8 max_bonding_count Maximum allowed bonding count. Range: 1 to 32
5 uint8 policy_flags Bonding policy. Values:
  • 0: If database is full, new bonding attempts will fail
  • 1: New bonding will overwrite the oldest existing bonding
  • 2: New bonding will overwrite longest time ago used existing bonding

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x02 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes

API

/* Function */
struct gecko_msg_sm_store_bonding_configuration_rsp_t *gecko_cmd_sm_store_bonding_configuration(uint8 max_bonding_count, uint8 policy_flags);

/* Response id */
gecko_rsp_sm_store_bonding_configuration_id

/* Response structure */
struct gecko_msg_sm_store_bonding_configuration_rsp_t
{
  uint16 result
}

sm_use_sc_oob

This command can be used to enable the use of OOB data (out-of-band encryption data) for a device for secure connections pairing. The enabling will genarate new OOB data and confirm values which can be sent to the remote device. After enabling the secure connections OOB data, the remote devices OOB data can be set with sm_set_sc_remote_oob_data. Calling this function will erase any set remote device OOB data and confirm values. The device will not allow any other kind of bonding if OOB data is set. The secure connections OOB data cannot be enabled simultaneously with legacy pairing OOB data.

Command

Byte Type Name Description
0 0x20 hilen Message type: Command
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x11 method Message ID
4 uint8 enable Enable OOB with secure connections pairing. Values:
  • 0: disable
  • 1: enable

Response

Byte Type Name Description
0 0x20 hilen Message type: Response
1 0x03 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x11 method Message ID
4-5 uint16 result Result code
  • 0: success
  • Non-zero: an error occurred
For other values refer to the Error codes
6 uint8array oob_data OOB data. 32-byte array. First 16-bytes contain randomly generated OOB data and last 16-bytes confirm value.

API

/* Function */
struct gecko_msg_sm_use_sc_oob_rsp_t *gecko_cmd_sm_use_sc_oob(uint8 enable);

/* Response id */
gecko_rsp_sm_use_sc_oob_id

/* Response structure */
struct gecko_msg_sm_use_sc_oob_rsp_t
{
  uint16 result,
  uint8array oob_data
}

sm events

sm_passkey_display

This event indicates a request to display the passkey to the user.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x05 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x00 method Message ID
4 uint8 connection Connection handle
5-8 uint32 passkey Passkey. Range: 0 to 999999.
  • NOTE! When displaying the passkey to the user, prefix the number with zeros in order to obtain a 6 digit number
  • Example: Passkey value is 42
  • Number to display to user is 000042

API

/* event id*/
gecko_evt_sm_passkey_display_id

/* event structure*/
struct gecko_msg_sm_passkey_display_evt_t
{
  uint8 connection,
  uint32 passkey
}

sm_passkey_request

This event indicates a request for the user to enter the passkey displayed on the remote device. Use the command sm_enter_passkey to input the passkey value.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x01 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x01 method Message ID
4 uint8 connection Connection handle

API

/* event id*/
gecko_evt_sm_passkey_request_id

/* event structure*/
struct gecko_msg_sm_passkey_request_evt_t
{
  uint8 connection
}

sm_confirm_passkey

This event indicates a request to display the passkey to the user and for the user to confirm the displayed passkey. Use the command sm_passkey_confirm to accept or reject the displayed passkey.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x05 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x02 method Message ID
4 uint8 connection Connection handle
5-8 uint32 passkey Passkey. Range: 0 to 999999.
  • NOTE! When displaying the passkey to the user, prefix the number with zeros in order to obtain a 6 digit number
  • Example: Passkey value is 42
  • Number to display to user is 000042

API

/* event id*/
gecko_evt_sm_confirm_passkey_id

/* event structure*/
struct gecko_msg_sm_confirm_passkey_evt_t
{
  uint8 connection,
  uint32 passkey
}

sm_bonded

This event is triggered after the pairing or bonding procedure has been successfully completed.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x03 method Message ID
4 uint8 connection Connection handle
5 uint8 bonding Bonding handle. Values:
  • 0xff: Pairing completed without bonding - the pairing key will be discarded after disconnection.
  • Other: Procedure completed, pairing key stored with given bonding handle

API

/* event id*/
gecko_evt_sm_bonded_id

/* event structure*/
struct gecko_msg_sm_bonded_evt_t
{
  uint8 connection,
  uint8 bonding
}

sm_bonding_failed

This event is triggered if the pairing or bonding procedure has failed.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x03 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x04 method Message ID
4 uint8 connection Connection handle
5-6 uint16 reason Describes error that occurred

API

/* event id*/
gecko_evt_sm_bonding_failed_id

/* event structure*/
struct gecko_msg_sm_bonding_failed_evt_t
{
  uint8 connection,
  uint16 reason
}

sm_list_bonding_entry

This event is triggered by the command sm_list_all_bondings if bondings exist in the local database.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x08 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x05 method Message ID
4 uint8 bonding Bonding handle
5-10 bd_addr address Bluetooth address of the remote device
11 uint8 address_type Address type

API

/* event id*/
gecko_evt_sm_list_bonding_entry_id

/* event structure*/
struct gecko_msg_sm_list_bonding_entry_evt_t
{
  uint8 bonding,
  bd_addr address,
  uint8 address_type
}

sm_list_all_bondings_complete

This event is triggered by the sm_list_all_bondings and follows sm_list_bonding_entry events.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x00 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x06 method Message ID

API

/* event id*/
gecko_evt_sm_list_all_bondings_complete_id

/* event structure*/
struct gecko_msg_sm_list_all_bondings_complete_evt_t
{
}

sm_confirm_bonding

This event indicates a request to display that new bonding request has been received to the user and for the user to confirm the request. Use the command sm_bonding_confirm to accept or reject the bonding request.

Event

Byte Type Name Description
0 0xa0 hilen Message type: Event
1 0x02 lolen Minimum payload length
2 0x0f class Message class:Security Manager
3 0x09 method Message ID
4 uint8 connection Connection handle
5 int8 bonding_handle Bonding handle for the request. Range: -1 to 31.
  • NOTE! When the bonding handle is anything else than -1 there is already existing bonding for this connection. Overwriting existing bonding is potential security risk.

API

/* event id*/
gecko_evt_sm_confirm_bonding_id

/* event structure*/
struct gecko_msg_sm_confirm_bonding_evt_t
{
  uint8 connection,
  int8 bonding_handle
}

sm enumerations

sm_bonding_key

These values define the bonding information of the bonded device stored in persistent store.

Enumerations

Value Name Description
1 sm_bonding_key_ltk LTK saved in master
2 sm_bonding_key_addr_public Public Address
4 sm_bonding_key_addr_static Static Address
8 sm_bonding_key_irk Identity resolving key for resolvable private addresses
16 sm_bonding_key_edivrand EDIV+RAND received from slave
32 sm_bonding_key_csrk Connection signature resolving key
64 sm_bonding_key_masterid EDIV+RAND sent to master

sm_io_capability

These values define the security management related I/O capabilities supported by the device

Enumerations

Value Name Description
0 sm_io_capability_displayonly Display Only
1 sm_io_capability_displayyesno Display with Yes/No-buttons
2 sm_io_capability_keyboardonly Keyboard Only
3 sm_io_capability_noinputnooutput No Input and No Output
4 sm_io_capability_keyboarddisplay Display with Keyboard