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Message-ID: <ab97d661-9054-4053-88ec-1b3a8db698dd@leemhuis.info>
Date: Thu, 6 Jun 2024 15:36:11 +0200
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Subject: Re: [REGRESSION][BISECTED] wifi: RTL8821CE does not work in monitor
 mode
To: Johannes Berg <johannes.berg@intel.com>, Kalle Valo <kvalo@kernel.org>
Cc: linux-wireless@vger.kernel.org, Savyasaachi Vanga
 <savyasaachiv@gmail.com>, Christian Heusel <christian@heusel.eu>,
 regressions@lists.linux.dev, Ping-Ke Shih <pkshih@realtek.com>,
 netdev <netdev@vger.kernel.org>
References: <chwoymvpzwtbmzryrlitpwmta5j6mtndocxsyqvdyikqu63lon@gfds653hkknl>
From: Thorsten Leemhuis <regressions@leemhuis.info>
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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/

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