Settings (Config) Management Group

Settings management group (known as Configuration Manager in the original MCUmgr repository) defines the following commands:

`Command ID`	Command description
`0`	Read/write setting
`1`	Delete setting
`2`	Commit settings
`3`	Load/Save settings

Note that the Zephyr version adds additional commands and features which are not supported by the original upstream version, however, the original client functionality should work for read/write functionality.

Read/write setting command

Read/write setting command allows updating a setting entry on a device or getting the current value of a setting from a device.

Read setting request

Read setting request header fields:

`OP`	`Group ID`	`Command ID`
`0`	`3`	`0`

CBOR data of request:

{
    (str)"name"         : (str)
    (str,opt)"max_size" : (uint)
}

where:

“name”	string of the setting to retrieve
“max_size”	optional maximum size of data to return

Read setting response

Read setting response header fields:

`OP`	`Group ID`	`Command ID`
`1`	`3`	`0`

CBOR data of successful response:

{
    (str)"val"          : (bstr)
    (str,opt)"max_size" : (uint)
}

In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“val”	binary string of the returned data, note that the underlying data type cannot be specified through this and must be known by the client.
“max_size”	will be set if the maximum supported data size is smaller than the maximum requested data size, and contains the maximum data size which the device supports, equivalent to kconfig:option:CONFIG_MCUMGR_GRP_SETTINGS_NAME_LEN.
“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Write setting request

Write setting request header fields:

`OP`	`Group ID`	`Command ID`
`2`	`3`	`0`

CBOR data of request:

{
    (str)"name"    : (str)
    (str)"val"     : (bstr)
}

where:

“name”	string of the setting to update/set
“val”	value to set the setting to

Write setting response

Write setting response header fields:

`OP`	`Group ID`	`Command ID`
`3`	`3`	`0`

The command sends an empty CBOR map as data if successful. In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Delete setting command

Delete setting command allows deleting a setting on a device.

Delete setting request

Delete setting request header fields:

`OP`	`Group ID`	`Command ID`
`2`	`3`	`1`

CBOR data of request:

{
    (str)"name"   : (str)
}

where:

“name”

string of the setting to delete

Delete setting response

Delete setting response header fields:

`OP`	`Group ID`	`Command ID`
`3`	`3`	`1`

The command sends an empty CBOR map as data if successful. In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Commit settings command

Commit settings command allows committing all settings that have been set but not yet applied on a device.

Commit settings request

Commit settings request header fields:

`OP`	`Group ID`	`Command ID`
`2`	`3`	`2`

The command sends sends empty CBOR map as data.

Commit settings response

Commit settings response header fields:

`OP`	`Group ID`	`Command ID`
`3`	`3`	`2`

The command sends an empty CBOR map as data if successful. In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Load/Save settings command

Load/Save settings command allows loading/saving all serialized items from/to persistent storage on a device.

Load settings request

Load settings request header fields:

`OP`	`Group ID`	`Command ID`
`0`	`3`	`3`

The command sends sends empty CBOR map as data.

Load settings response

Load settings response header fields:

`OP`	`Group ID`	`Command ID`
`1`	`3`	`3`

The command sends an empty CBOR map as data if successful. In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Save settings request

Save settings request header fields:

`OP`	`Group ID`	`Command ID`
`2`	`3`	`3`

The command sends sends empty CBOR map as data.

Save settings response

Save settings response header fields:

`OP`	`Group ID`	`Command ID`
`3`	`3`	`3`

The command sends an empty CBOR map as data if successful. In case of error the CBOR data takes the form:

{
    (str)"err" : {
        (str)"group"    : (uint)
        (str)"rc"       : (uint)
    }
}

{
    (str)"rc"       : (int)
}

where:

“err” -> “group”	`mcumgr_group_t` group of the group-based error code. Only appears if an error is returned when using SMP version 2.
“err” -> “rc”	contains the index of the group-based error code. Only appears if non-zero (error condition) when using SMP version 2.
“rc”	`mcumgr_err_t` only appears if non-zero (error condition) when using SMP version 1.

Settings access callback

There is a settings access MCUmgr callback available (see MCUmgr Callbacks for details on callbacks) which allows for applications/modules to know when settings management commands are used and, optionally, block access (for example through the use of a security mechanism). This callback can be enabled with CONFIG_MCUMGR_GRP_SETTINGS_ACCESS_HOOK, registered with the event MGMT_EVT_OP_SETTINGS_MGMT_ACCESS, whereby the supplied callback data is settings_mgmt_access.