Re: [PATCH] wifi: mac80211: do not set 320MHz EHT capabilities on non 6GHz band

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2026-01-22 at 15:56 +0100, Nicolas Escande wrote:
> The spec (at least 802.11-be draft7) at section 9.4.2.323.3 says we should
> not set the 320MHz related fields when not operating on a 6GHz band. It's
> quite explicit for most of them. For example:
> 
> Bit 0 "Support For 320 MHz In 6 GHz" says "Reserved if the EHT
>       Capabilities element is indicating capabilities for the 2.4 GHz or
>       5 GHz bands."
> 
> Bit 22-24 "Number Of Sounding Dimensions (= 320 MHz)" says "Reserved if
>           the SU Beamformer subfield is 0 or the Support For 320 MHz In
>           6 GHz subfield in EHT Capabilities Information field does not
>           indicate support for a bandwidth of 320 MHz."
> 
> Bit 54 "Support Of EHT-MCS 15 In MRU" says about bit 3 "If 320 MHz is not
>         supported, then B3 is set to 0."
> 
> For bit 13-15 "Beamformee SS (= 320 MHz)" it's not explicit, but it makes
> little sense to special case the handling of this one.

Sure, but ...

> Fixes: 6239da18d2f9 ("wifi: mac80211: adjust EHT capa when lowering bandwidth")
> Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
> ---
>  net/mac80211/util.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mac80211/util.c b/net/mac80211/util.c
> index 0c46009a3d63..996983f6815b 100644
> --- a/net/mac80211/util.c
> +++ b/net/mac80211/util.c
> @@ -4426,7 +4426,8 @@ int ieee80211_put_eht_cap(struct sk_buff *skb,
>  			~IEEE80211_EHT_PHY_CAP6_MCS15_SUPP_160MHZ;
>  	}
>  
> -	if (conn->bw_limit < IEEE80211_CONN_BW_LIMIT_320) {
> +	if (conn->bw_limit < IEEE80211_CONN_BW_LIMIT_320 ||
> +	    sband->band != NL80211_BAND_6GHZ) {
>  		fixed.phy_cap_info[0] &=
>  			~IEEE80211_EHT_PHY_CAP0_320MHZ_IN_6GHZ;
>  		fixed.phy_cap_info[1] &=

How does this make any sense? The driver should just not advertise the
bit on its 2.4 and 5 GHz sbands?

johannes