CONFIG_BT_CTRL_DATA_LENGTH_MAX is set to 251 but compilation reports set to ''

[Geir Strand]

Hi,

We are using an nRF5340 and nRF Connect SDK v2.6.2. We have set CONFIG_BT_BUF_ACL_RX_SIZE to more than 251 and BT_CTLR_DATA_LENGTH_MAX to 251 in our prj.conf. 

When compiling our code we get the following compilation warning (from app core compilation it seems):

warning: BT_CTLR_DATA_LENGTH_MAX (defined at
/home/surendra/ncs/v2.6.2/nrf/samples/common/mcumgr_bt_ota_dfu/Kconfig:131,
/home/surendra/ncs/v2.6.2/nrf/subsys/bluetooth/services/fast_pair/Kconfig.fast_pair:101,
subsys/bluetooth/controller/Kconfig:490) was assigned the value '251' but got the value ''. See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_BT_CTLR_DATA_LENGTH_MAX and/or look up
BT_CTLR_DATA_LENGTH_MAX in the menuconfig/guiconfig interface. The Application Development Primer,
Setting Configuration Values, and Kconfig - Tips and Best Practices sections of the manual might be
helpful too.

I have checked our build folder and both KCONFIGs are  set correctly in the multiprotocol_rpmsg folder but on the app processor (zephyr) it is not set. Is this correct behavior? If it is not needed in the app processor, should this warning not be removed? Moving the KCONFIGs to the child_image seems wrong if we are to change from nRF53 to another family..

Best regards,

Geir Strand

[Einar Thorsrud]

Hi,

These are Bluetooth controller configurations, and on the nRF5340 the controller runs on the network core, so these configs are only valid  on the netwok conr efirmware (hci_ipc). I suspect you added them to the configuration of the main application runing on the app core? Instead, you should add it in a child_image configuration file as you can see an example of in the throughput sample: hci_ipc.conf.

Moving the KCONFIGs to the child_image seems wrong if we are to change from nRF53 to another family..

Then you must use a separate config file for the other board, as on the nRF5340, this must be in the network core configuration.