hci_uart with Channel Sounding feature enabled

[nychyporuk]

I am building a Bluetooth controller with channel sounding feature enabled. The project uses an external Bluetooth host along with the hci_uart example. The prj.conf file was modified to enable CONFIG_BT_CHANNEL_SOUNDING.

However, when I try to send the bt_le_cs_read_local_supported_capabilities command, I receive a status of "Command Disallowed".

Below are the hex commands exchanged:

• Command sent (HCI Command Packet):
  01 89 20 00

• Response received (HCI Event Packet):
  04 0e 20 01 89 20 0c 00 00 00 00 00 00 90 0a 00 00 e4 00 0c 00 28 22 c0 00 00 00 e0 00 04 18 82 f7 ff ff

Could you please advise if I am doing something wrong? Does this command require any preconditions or additional configuration steps?

Thank you for your assistance.

[ivan iushkov]

Probably it happens due to this requirement from Core Specification:

```

If the Host issues this command when the Channel Sounding (Host Support) feature bit
(see [Vol 6] Part B, Section 4.6.33.4) is not set, then the Controller shall return the error
code Command Disallowed (0x0C).

```

I guess Host needs to enable CS (Host Support) feature bit first.

In Zephyr Host it is done here:

https://github.com/nrfconnect/sdk-zephyr/blob/10ab9b6c55c196abec008f3cd0c0d2560a70be1f/subsys/bluetooth/host/hci_core.c#L3670 

[nychyporuk]

Thank you, ivan iushkov !

That's the part I was missing. Now it works as expected!