Re: [REGRESSION][BISECTED] wifi: RTL8821CE does not work in monitor mode

On 28.05.24 00:01, Christian Heusel wrote:

Savyasaachi reports that scanning for other stations in monitor mode
does not work anymore with his RTL8821CE wireless network card for linux
kernels after 6.8.9.

His workflow was putting the adapter in monitor mode by running
"airmon-ng start wlan0" and then capture the surrounding stations with
"airodump-ng wlan0".

We have bisected the issue together in the issue in the Arch Linux
bugtracker[0] down to the following commit:

    0a44dfc070749 ("wifi: mac80211: simplify non-chanctx drivers")

Johannes, Kalle, if you have a minute, what's the overall situation
regarding that commit and related regression fixes for drivers that are
affected by it?

Afaics it is like this:

One regression caused by that commit was already fixed with
2f7cf3b61d8522 ("wifi: mt76: mt7915: add missing chanctx ops"); two more
will soon be fixed once 2f7cf3b61d8522 ("wifi: mt76: mt7915: add missing
chanctx ops") and 819bda58e77bb6 ("wifi: rtlwifi: Ignore
IEEE80211_CONF_CHANGE_RETRY_LIMITS") are mainlined.

But there was no reply to the regression report this thread is about.
And Ping-Ke from Realtek even wrote "We have a draft fix of rtw88 driver
for RTL8821CE, but as mentioned some drivers are affected, so I don't
plan to send out the patch." So apparently Ping-Ke is waiting for some
statement from you how to proceed.
https://lore.kernel.org/all/0e65ca6b471b4186a370b9a57de11abe@realtek.com/ (local)

There there is another report about problems caused by this patch where
the user has a mt7601u -- but also broadly (and thus likely incorrectly)
claims that all drivers are affected:
https://bugzilla.kernel.org/show_bug.cgi?id=218884 (I mentioned that
report a few days ago in this thread already without any reaction so far
afaics).

That all looks a bit concerning (and makes me wonder if temporary
reverting 0a44dfc070749 might be wise). :-/ But I might be missing
something here, that's why it would be good if you could provide a quick
evaluation of the situation.

Ciao, Thorsten