Re: [PATCH v4 6/8] Bluetooth: hci_sync: Add NVMEM-backed BD address retrieval

[Dmitry Baryshkov]

On Tue, Jun 09, 2026 at 09:52:31AM +0200, Loic Poulain wrote:
> Some devices store the Bluetooth BD address in non-volatile
> memory, which can be accessed through the NVMEM framework.
> Similar to Ethernet or WiFi MAC addresses, add support for
> reading the BD address from a 'local-bd-address' NVMEM cell.
> 
> As with the device-tree provided BD address, add a quirk to
> indicate whether a device or platform should attempt to read
> the address from NVMEM when no valid in-chip address is present.
> Also add a quirk to indicate if the address is stored in
> big-endian byte order.
> 
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>
> ---
>  include/net/bluetooth/hci.h | 18 ++++++++++++++++++
>  net/bluetooth/hci_sync.c    | 39 ++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 56 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 572b1c620c5d653a1fe10b26c1b0ba33e8f4968f..7686466d1109253b0d75edeb5f6a99fb98ce4cc6 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -164,6 +164,24 @@ enum {
>  	 */
>  	HCI_QUIRK_BDADDR_PROPERTY_BROKEN,
>  
> +	/* When this quirk is set, the public Bluetooth address
> +	 * initially reported by HCI Read BD Address command
> +	 * is considered invalid. The public BD Address can be
> +	 * retrieved via a 'local-bd-address' NVMEM cell.

Why do we need a quirk here? Can't we always assume that if there is an
NVMEM cell, it contains a correct address, even if HCI command returned
a seemingly-sensible one?

> +	 *
> +	 * This quirk can be set before hci_register_dev is called or
> +	 * during the hdev->setup vendor callback.
> +	 */
> +	HCI_QUIRK_USE_BDADDR_NVMEM,
> +
> +	/* When this quirk is set, the Bluetooth Device Address provided by
> +	 * the 'local-bd-address' NVMEM is stored in big-endian order.
> +	 *
> +	 * This quirk can be set before hci_register_dev is called or
> +	 * during the hdev->setup vendor callback.
> +	 */
> +	HCI_QUIRK_BDADDR_NVMEM_BE,

Also, is this necessary? Are the devices which store the address in the
wrong format in the NVMEM?

> +
>  	/* When this quirk is set, the duplicate filtering during
>  	 * scanning is based on Bluetooth devices addresses. To allow
>  	 * RSSI based updates, restart scanning if needed.

-- 
With best wishes
Dmitry