Hans de Goede [off-list ref] wrote:

This is a second attempt at honering the country code send out by access
points. This was first added in commit b0b524f079a2 ("brcmfmac: use
ISO3166 country code and 0 rev as fallback").

Subsequently this was reverted in commit 151a7c12c4fc ("Revert "brcmfmac:
use ISO3166 country code and 0 rev as fallback""), because it was causing
issues with AP mode on some brcmfmac models (specifically on BCM4359/9).

Many devices ship with a nvram ccode value of X2/XT/XU/XV/ALL which are
all special world-wide compatibility ccode-s. Most of these world-wide
ccode-s allow passive scan mode only for 2.4GHz channels 12-14,
only enabling them when an AP is seen on them.

But at least on brcmfmac43455 devices this is not working correctly, these
do not see accesspoints on channels 12-14 unless the ccode is changes to
a country where these channels are allowed.

Translating received country codes to an ISO3166 country code and 0 rev
ccreq fixes devices using a brcmfmac43455 with a X2/XT/XU/XV/ALL ccode
not seeing accesspoints on channels 12-14.

To avoid this causing issues on other brcmfmac models again, the
fallback is limited to only brcmfmac4345* chips this time.

Cc: Shawn Guo <redacted>
Cc: Soeren Moch <redacted>
Cc: Fabio Aiuto <redacted>
Signed-off-by: Hans de Goede <redacted>

Arend, can you take a look?

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20211218185643.158182-1-hdegoede@redhat.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches