Having disabled a BCM43142A0 Bluetooth adapter, how do I remove the proprietary kernel blob?

Question

I've successfully disabled my laptop's internal Broadcom Bluetooth adapter using this procedure. All is now working fine with my replacement (non-Broadcom) external Bluetooth adapter. However, I think the now-disabled adapter was probably being driven by a proprietary kernel blob that I installed a long time ago with b43-fwcutter. Can I safely remove that blob, and if so how, please?

The b43-fwcutter is just a way to install Broadcom wifi firmware, it shouldn't cause any issues. Do you want to disable the Broadcom wifi? — Jeremy31, Apr 08 '23 at 17:42
@Jeremy31 Yes, in fact I've already disabled the Broadcom wifi. Bit hazy on how I did that, possibly by apt removing bcmwl-kernel-source. The Broadcom Bluetooth was unaffected by that, though. — Daniel Hatton, Apr 08 '23 at 18:53
AH, OK. The manpage for b43-fwcutter just says it's for "Broadcom 43xx hardware", it forgets to specify "only the wifi bits". Nevertheless, I still (probably) find myself with a blob in my kernel from when I was using the wifi adapter, and would still kind of like to remove said blob. — Daniel Hatton, Apr 09 '23 at 14:47
It is much easier to simply blacklist the module(s). Please run: lsmod and paste the result here and give us the link: http://paste.ubuntu.com — chili555, Apr 09 '23 at 19:39
@chili555 Thanks. That paste site appears to require an Ubuntu One account, and ISTR reading the Ubuntu One Terms of Use a couple of years ago and thinking "no way". I have bcma and (probably irrelevant) btbcm loaded. — Daniel Hatton, Apr 10 '23 at 11:20

chili555 · Accepted Answer · 2023-04-11T13:33:38.507

2

I suggest that you blacklist bcma.

sudo -i
echo "blacklist bcma"  >>  /etc/modprobe.d/blacklist.conf
modprobe -r bcma
exit

Now check:

sudo lshw -C network

Your Broadcom wireless device should now appear as UNCLAIMED.

EDIT: Please try:

sudo modprobe -r bcma
sudo modprobe -r cfg80211
sudo update-initramfs -u

Reboot.

edited Apr 11 '23 at 13:33

answered Apr 10 '23 at 13:27

chili555

60,188

It does indeed, thanks. I'll see later if the UNCLAIMED-ness survives a reboot (blacklisting sometimes seems to be ignored for modules that are loaded as dependencies of another module). – Daniel Hatton Apr 10 '23 at 15:50
Oof. After a reboot, the "UNCLAIMED" has gone away and lsmod reveals bcma is loaded again. I've checked, and the relevant line is definitely present in /etc/modprobe.d/blacklist.conf. – Daniel Hatton Apr 10 '23 at 23:44
Please check again: lsmod Are any of these loaded? cfg80211,mac80211,ssb,bcma,cordic or b43? – chili555 Apr 11 '23 at 01:26
Yes: cfg80211 and bcma. – Daniel Hatton Apr 11 '23 at 07:51
Please see my edit in a few moments. – chili555 Apr 11 '23 at 13:29
Thanks. Should I also add cfg80211 to blacklist.conf? – Daniel Hatton Apr 11 '23 at 14:43
Do you have another wireless device? USB, perhaps? Does it also depend on cfg80211? – chili555 Apr 11 '23 at 14:45
1

Ah: when I try to modprobe -r cfg80211, I get a complaint that the module is in use by 88x2bu, which does indeed relate to the chipset in my new USB wifi interface. – Daniel Hatton Apr 11 '23 at 17:04

Having disabled a BCM43142A0 Bluetooth adapter, how do I remove the proprietary kernel blob?

1 Answers1