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From:   Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
To:     Johannes Berg <johannes@sipsolutions.net>,
        ath11k@lists.infradead.org
Cc:     linux-wireless@vger.kernel.org,
        Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Subject: [PATCH 1/9] cfg80211: Add new channel flag to identify 6GHz PSC channel
Date:   Mon, 18 May 2020 09:44:16 -0700
Message-Id: <20200518164424.29497-2-pradeepc@codeaurora.org>
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6GHz channels are divided into preferred scanning channels(PSC)
and non-PSC channels. One in every four 20MHz channels is a PSC.
Spec mandates to use only PSC channels as primary channels for
setting up BSS on 6GHz only AP.

The set of 20 MHz channels in the 6 GHz band, with channel center
frequency, ch_a = Channel starting frequency – 55 + 80 × n (MHz)
are referred to as preferred scanning channels (PSCs) where,
n = 1, …, 15 as per IEEE P802.11ax/D6.0.

This flag also will be used when making scanning decision on
6GHz channels.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
---
 include/net/cfg80211.h |  2 ++
 net/wireless/reg.c     | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index fd6a973b1249..ca3e9df7adfe 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -96,6 +96,7 @@ struct wiphy;
  * @IEEE80211_CHAN_NO_10MHZ: 10 MHz bandwidth is not permitted
  *	on this channel.
  * @IEEE80211_CHAN_NO_HE: HE operation is not permitted on this channel.
+ * @IEEE80211_CHAN_PSC: 6GHz Channel is Preferred Scanning Channel(PSC)
  *
  */
 enum ieee80211_channel_flags {
@@ -113,6 +114,7 @@ enum ieee80211_channel_flags {
 	IEEE80211_CHAN_NO_20MHZ		= 1<<11,
 	IEEE80211_CHAN_NO_10MHZ		= 1<<12,
 	IEEE80211_CHAN_NO_HE		= 1<<13,
+	IEEE80211_CHAN_PSC		= 1<<14,
 };
 
 #define IEEE80211_CHAN_NO_HT40 \
diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 0d74a31ef0ab..4ebaa57e60e4 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -2023,6 +2023,21 @@ static bool is_ht40_allowed(struct ieee80211_channel *chan)
 	return true;
 }
 
+static bool reg_is_6ghz_channel_psc(struct ieee80211_channel *chan)
+{
+	/*
+	 * From IEEE P802.11ax/D6.0: The set of 20 MHz channels in the 6 GHz
+	 * band, with channel center frequency, ch_a = Channel starting
+	 * frequency – 55 + 80 × n (MHz) are referred to as preferred scanning
+	 * channels (PSCs). Channel starting frequency is defined in 27.3.23.2
+	 * (Channel allocation in the 6 GHz band), and n = 1, …, 15.
+	 */
+	if (!(((chan->center_freq - 5940 + 55) >> 4) % 5))
+		return true;
+
+	return false;
+}
+
 static void reg_process_ht_flags_channel(struct wiphy *wiphy,
 					 struct ieee80211_channel *channel)
 {
@@ -2305,6 +2320,10 @@ static void handle_channel_custom(struct wiphy *wiphy,
 	else
 		chan->flags |= map_regdom_flags(reg_rule->flags) | bw_flags;
 
+	if (chan->band == NL80211_BAND_6GHZ &&
+	    reg_is_6ghz_channel_psc(chan))
+		chan->flags |= IEEE80211_CHAN_PSC;
+
 	chan->max_antenna_gain = (int) MBI_TO_DBI(power_rule->max_antenna_gain);
 	chan->max_reg_power = chan->max_power =
 		(int) MBM_TO_DBM(power_rule->max_eirp);
-- 
2.17.1