Re: [PATCH v2 03/22] cfg80211: regulatory: handle S1G channels

From: Thomas Pedersen <thomas@adapt-ip.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH v2 03/22] cfg80211: regulatory: handle S1G channels
Date: Sat, 05 Sep 2020 11:38:42 -0700	[thread overview]
Message-ID: <44089020f46d6164de74318bddc2bc9e@adapt-ip.com> (raw)
In-Reply-To: <20200831205600.21058-4-thomas@adapt-ip.com>

On 2020-08-31 13:55, Thomas Pedersen wrote:
> S1G channels have a minimum bandwidth of 1Mhz, and there
> is a 1:1 mapping of allowed bandwidth to channel number.
> 
> Signed-off-by: Thomas Pedersen <thomas@adapt-ip.com>
> 
> ---
> 
> v2:
>  - drop the freq_reg_info() interface changes and move the
>    check for S1G band inside. Fixes a driver compile
>    error.
>  - fix iterating past bws[] in __freq_reg_info() by
>    setting initial element to 0.
>    Reported-by: kernel test robot <lkp@intel.com>
> ---
>  net/wireless/reg.c | 70 ++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 58 insertions(+), 12 deletions(-)
> 
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index 0ab7808fcec8..be6f54b70ad3 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -1617,9 +1617,11 @@ __freq_reg_info(struct wiphy *wiphy, u32
> center_freq, u32 min_bw)
>  {
>  	const struct ieee80211_regdomain *regd = reg_get_regdomain(wiphy);
>  	const struct ieee80211_reg_rule *reg_rule = NULL;
> +	const u32 bws[] = {0, 1, 2, 4, 5, 8, 10, 16, 20};
> +	int i = sizeof(bws) / sizeof(u32) - 1;

This could be 'int i = ARRAY_SIZE(bws) - 1'.

>  	u32 bw;
> 
> -	for (bw = MHZ_TO_KHZ(20); bw >= min_bw; bw = bw / 2) {
> +	for (bw = MHZ_TO_KHZ(bws[i]); bw >= min_bw; bw = 
> MHZ_TO_KHZ(bws[i--])) {
>  		reg_rule = freq_reg_info_regd(center_freq, regd, bw);
>  		if (!IS_ERR(reg_rule))
>  			return reg_rule;
> @@ -1631,7 +1633,9 @@ __freq_reg_info(struct wiphy *wiphy, u32
> center_freq, u32 min_bw)
>  const struct ieee80211_reg_rule *freq_reg_info(struct wiphy *wiphy,
>  					       u32 center_freq)
>  {
> -	return __freq_reg_info(wiphy, center_freq, MHZ_TO_KHZ(20));
> +	u32 min_bw = center_freq < MHZ_TO_KHZ(1000) ? 1 : 20;
> +
> +	return __freq_reg_info(wiphy, center_freq, MHZ_TO_KHZ(min_bw));
>  }
>  EXPORT_SYMBOL(freq_reg_info);
> 
> @@ -1659,6 +1663,7 @@ static uint32_t reg_rule_to_chan_bw_flags(const
> struct ieee80211_regdomain *regd
>  {
>  	const struct ieee80211_freq_range *freq_range = NULL;
>  	u32 max_bandwidth_khz, center_freq_khz, bw_flags = 0;
> +	bool is_s1g = chan->band == NL80211_BAND_S1GHZ;
> 
>  	freq_range = &reg_rule->freq_range;
> 
> @@ -1678,16 +1683,57 @@ static uint32_t
> reg_rule_to_chan_bw_flags(const struct ieee80211_regdomain *regd
>  					MHZ_TO_KHZ(20)))
>  		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
> 
> -	if (max_bandwidth_khz < MHZ_TO_KHZ(10))
> -		bw_flags |= IEEE80211_CHAN_NO_10MHZ;
> -	if (max_bandwidth_khz < MHZ_TO_KHZ(20))
> -		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
> -	if (max_bandwidth_khz < MHZ_TO_KHZ(40))
> -		bw_flags |= IEEE80211_CHAN_NO_HT40;
> -	if (max_bandwidth_khz < MHZ_TO_KHZ(80))
> -		bw_flags |= IEEE80211_CHAN_NO_80MHZ;
> -	if (max_bandwidth_khz < MHZ_TO_KHZ(160))
> -		bw_flags |= IEEE80211_CHAN_NO_160MHZ;
> +	if (is_s1g) {
> +		/* S1G is strict about non overlapping channels. We can
> +		 * calculate which bandwidth is allowed per channel by finding
> +		 * the largest bandwidth which cleanly divides the freq_range.
> +		 */
> +		int edge_offset;
> +		int ch_bw = max_bandwidth_khz;
> +
> +		while (ch_bw) {
> +			edge_offset = (center_freq_khz - ch_bw / 2) -
> +				      freq_range->start_freq_khz;
> +			if (edge_offset % ch_bw == 0) {
> +				switch (KHZ_TO_MHZ(ch_bw)) {
> +				case 1:
> +					bw_flags |= IEEE80211_CHAN_1MHZ;
> +					break;
> +				case 2:
> +					bw_flags |= IEEE80211_CHAN_2MHZ;
> +					break;
> +				case 4:
> +					bw_flags |= IEEE80211_CHAN_4MHZ;
> +					break;
> +				case 8:
> +					bw_flags |= IEEE80211_CHAN_8MHZ;
> +					break;
> +				case 16:
> +					bw_flags |= IEEE80211_CHAN_16MHZ;
> +					break;
> +				default:
> +					/* If we got here, no bandwidths fit on
> +					 * this frequency, ie. band edge.
> +					 */
> +					bw_flags |= IEEE80211_CHAN_DISABLED;
> +					break;
> +				}
> +				break;
> +			}
> +			ch_bw /= 2;
> +		}
> +	} else {
> +		if (max_bandwidth_khz < MHZ_TO_KHZ(10))
> +			bw_flags |= IEEE80211_CHAN_NO_10MHZ;
> +		if (max_bandwidth_khz < MHZ_TO_KHZ(20))
> +			bw_flags |= IEEE80211_CHAN_NO_20MHZ;
> +		if (max_bandwidth_khz < MHZ_TO_KHZ(40))
> +			bw_flags |= IEEE80211_CHAN_NO_HT40;
> +		if (max_bandwidth_khz < MHZ_TO_KHZ(80))
> +			bw_flags |= IEEE80211_CHAN_NO_80MHZ;
> +		if (max_bandwidth_khz < MHZ_TO_KHZ(160))
> +			bw_flags |= IEEE80211_CHAN_NO_160MHZ;
> +	}
>  	return bw_flags;
>  }

-- 
thomas