Re: [PATCH wireless] wifi: cfg80211: return center freq for 1Mhz S1G chan start/end

[Johannes Berg <johannes@sipsolutions.net>]

^^ should be MHz in the subject

On Tue, 2025-10-21 at 22:07 +1100, Lachlan Hodges wrote:
> The frequencies returned by cfg80211_s1g_get_{start/end}_freq_khz()
> for 1MHz chandefs are off by +-1000KHz. 

Hmm. I'm confused.

> +++ b/include/net/cfg80211.h
> @@ -10194,7 +10194,8 @@ cfg80211_s1g_get_start_freq_khz(const struct cfg80211_chan_def *chandef)
>  	u32 bw_mhz = cfg80211_chandef_get_width(chandef);
>  	u32 center_khz =
>  		MHZ_TO_KHZ(chandef->center_freq1) + chandef->freq1_offset;
> -	return center_khz - bw_mhz * 500 + 500;
> +
> +	return (bw_mhz == 1) ? center_khz : center_khz - bw_mhz * 500 + 500;
>  }

I don't see how this changes anything - if "bw_mhz == 1" then

   center_freq - bw_mhz * 500 + 500
== center_freq -      1 * 500 + 500
== center_freq -          500 + 500
== center_freq

so this makes no difference?

>  
>  /**
> @@ -10209,7 +10210,8 @@ cfg80211_s1g_get_end_freq_khz(const struct cfg80211_chan_def *chandef)
>  	u32 bw_mhz = cfg80211_chandef_get_width(chandef);
>  	u32 center_khz =
>  		MHZ_TO_KHZ(chandef->center_freq1) + chandef->freq1_offset;
> -	return center_khz + bw_mhz * 500 - 500;
> +
> +	return (bw_mhz == 1) ? center_khz : center_khz + bw_mhz * 500 - 500;

Same here with the sign inverted?

What am I missing?

johannes