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

[Ping-Ke Shih <pkshih@realtek.com>]

Thorsten Leemhuis <regressions@leemhuis.info> wrote:
> On 28.05.24 10:21, Linux regression tracking (Thorsten Leemhuis) wrote:
> > 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.
> >> [...]
> 
> Hmm, the wifi developers did not reply to the inquiry quoted below. :-/
> Guess I'll have to take a closer look a the linked bugzilla report then.
> 
> Anyway: Christian, Savyasaachi, I noticed a submission of a patch
> referencing the culprit with a Fixes: tag; it talks about package loss,
> but it still made me wonder if that might be related somehow:
> https://lore.kernel.org/all/1fabb8e4-adf3-47ae-8462-8aea963bc2a5@gmail.com/
> 
> Ciao, Thorsten
> 
> > So back to the real problem:
> >
> > @wifi developers: Is there some bigger problem in 6.9.y related to
> > monitoring mode that is affecting a lot of drivers/users?
> >
> > I'm asking because I noticed another report that sounded related. To
> > quote: https://bugzilla.kernel.org/show_bug.cgi?id=218884
> >
> > """
> >>  Michael 2024-05-24 17:04:51 UTC
> >>
> >> Some features are broken since kernel 6.9.1 when running monitor mode.
> >>
> >> First bug:
> >> Switching a channel via "NL80211_ATTR_WIPHY_FREQ" does not switch the channel/frequency.
> >>
> >> That is not a device driver problem, because all device drivers (Mediatek, Ralink, Realtek, ...) are
> affected.

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. Instead we are looking for
the fix of cfg80211/mac80211. 

Ping-Ke