Bluetooth: Host: BT_DEVICE_NAME should be mutually exclusive with BT_DEVICE_NAME_DYNAMIC

[Thalley]

Summary

The 2 Kconfig options should be mutually exclusive, i.e. if CONFIG_BT_DEVICE_NAME_DYNAMIC=y, then CONFIG_BT_DEVICE_NAME should not be set-able.

The reason for this is to avoid cases where e.g. CONFIG_BT_DEVICE_NAME_DYNAMIC=y and applications mistakenly use CONFIG_BT_DEVICE_NAME when e.g. advertising instead of bt_get_name and may thus advertise the wrong name.

Describe the solution you'd like

Modify

config BT_DEVICE_NAME
	string "Bluetooth device name"
	default "Zephyr"
	help
	  Bluetooth device name. Name can be up to 248 bytes long (excluding
	  NULL termination). Can be empty string.

to be

config BT_DEVICE_NAME
	string "Bluetooth device name" if !BT_DEVICE_NAME_DYNAMIC
	default "Zephyr"
	default "" if BT_DEVICE_NAME_DYNAMIC
	help
	  Bluetooth device name. Name can be up to 248 bytes long (excluding
	  NULL termination). Can be empty string.

or

config BT_DEVICE_NAME
	string "Bluetooth device name" 
	depends on !BT_DEVICE_NAME_DYNAMIC
	default "Zephyr"
	help
	  Bluetooth device name. Name can be up to 248 bytes long (excluding
	  NULL termination). Can be empty string.

Alternatives

No response

Additional Context

No response

[axel-lebourhis]

Trickier than what it seems at first glance. Even host files like hci_core.c assume CONFIG_BT_DEVICE_NAME is always set and use it as a default value in bt_enable.
I saw there's already an open PR for this issue. If for any reason it doesn’t go through or needs additional work, I’d be happy to help or pick it up if needed — just let me know

[Thalley]

Trickier than what it seems at first glance. Even host files like hci_core.c assume CONFIG_BT_DEVICE_NAME is always set and use it as a default value in bt_enable. I saw there's already an open PR for this issue. If for any reason it doesn’t go through or needs additional work, I’d be happy to help or pick it up if needed — just let me know

Agreed. Removed the Good First Issue label. Requires quite some significant work, and probably even a migration guide entry.

[alwa-nordic]

Let's find a way to do this without breakage. I think the best way to do this is to deprecate CONFIG_BT_DEVICE_NAME now and introduce replacements. Let's discuss options for the replacement.

[alwa-nordic]

I think we can replace it with CONFIG_BT_GAP_DEVICE_NAME_CONSTANT, which will serve both for use with if defined() and also expand to the string constant. If it's possible to have strings be a choice in kconfig, then the other choice can be CONFIG_BT_GAP_DEVICE_NAME_DYNAMIC.