[PATCH V13 8/9] wifi: ath12k: add support for 160 MHz bandwidth

[Nicolas Escande]

On Wed May 21, 2025 at 11:38 PM CEST, Pradeep Kumar Chitrapu wrote:
[...]
> Thanks Nicolas,
>
> I believe IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ mean only 
> 80PLUS80 not both 160 and 80PLUS80 and STA must set 
> IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ flags for indicating 160 MHz 
> support. Please correct me if my understanding is correct. However I 
> agree that we must allow STA to connect irrespective of which flag STA 
> sets as long as bandwidth is 160MHz. I see ath10k and ath11k also allows 
> this by setting default phymode of MODE_11AC_VHT160 for BW 
> ==IEEE80211_STA_RX_BW_160 case.
> I will make this change in next revision.
> Thanks
> Pradeep

Hello Pradeep,

Well this is quite unclear for me maybe Johannes or someone more aware of the
evolutions of the standard could shime in.

>From what I've gathered:
  - the naming IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ implies both
    which points it was the case when added
  - and the original 802.11ac-2013 Table 8-183v states:
	Set to 0 if the STA does not support either 160 or 80+80 MHz.
	Set to 1 if the STA supports 160 MHz.
	Set to 2 if the STA supports 160 MHz and 80+80 MHz.
	The value 3 is reserved.

Things get complicated after:
 - later versions like 802.11-2020 have deprecated value 2 in favor of the new
   Extendeed NSS BW feature
 - Table 9-272 still implies both 160 & 80+80
 - Table 11-23 & Table 11-24 implies only 80+80 but both talk about the
   'VHT Operation' Channel Width field and not the 'VHT Capabilities' Supported
   Channel Width. And thoses had different values even in the first AC amendment

So it feels like when no Extended NSS BW Support is used (first gen AC devices),
IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ really means both 160 & 80+80