linux-kernel - [PATCH wireless-next 3/3] wifi: mac80211: Allow DFS/CSA on a radio if scan is ongoing on another radio

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Message-ID: <20250514-mlo-dfs-acs-v1-3-74e42a5583c6@quicinc.com>
Date: Wed, 14 May 2025 16:58:24 +0530
From: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>
To: Johannes Berg <johannes@...solutions.net>
CC: <linux-wireless@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Aditya
 Kumar Singh" <aditya.kumar.singh@....qualcomm.com>,
        Raj Kumar Bhagat
	<quic_rajkbhag@...cinc.com>
Subject: [PATCH wireless-next 3/3] wifi: mac80211: Allow DFS/CSA on a radio
 if scan is ongoing on another radio

From: Aditya Kumar Singh <aditya.kumar.singh@....qualcomm.com>

Currently, in multi-radio wiphy cases, if a scan is ongoing on one radio,
-EBUSY is returned when DFS or a channel switch is initiated on another
radio. Because of this, an MLD AP with one radio (link) in an ongoing scan
cannot initiate DFS or a channel switch on another radio (link).

In multi-radio wiphy cases, multiple radios are grouped under a single
wiphy. Hence, if a scan is ongoing on one underlying radio and DFS or a
channel switch is requested on a different underlying radio of the same
wiphy, these operations can be allowed simultaneously.

Add logic to check the underlying radio used for the ongoing scan. If the
radio on which DFS or a channel switch is requested is not being used for
the scan, allow the operation; otherwise, return -EBUSY.

Signed-off-by: Aditya Kumar Singh <aditya.kumar.singh@....qualcomm.com>
Signed-off-by: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>
---
 net/mac80211/cfg.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 2cd8731d8275b2f67c1b1305ec0bafc368a4498a..b76598abfb76708468432b3ec082955d4820e4a3 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3549,6 +3549,68 @@ static int ieee80211_set_bitrate_mask(struct wiphy *wiphy,
 	return 0;
 }
 
+static bool
+__ieee80211_is_scan_ongoing(struct wiphy *wiphy,
+			    struct ieee80211_local *local,
+			    struct cfg80211_chan_def *chandef)
+{
+	struct cfg80211_scan_request *scan_req;
+	int chan_radio_idx, req_radio_idx;
+	struct ieee80211_roc_work *roc;
+	bool ret = false;
+
+	if (!list_empty(&local->roc_list) || local->scanning)
+		ret = true;
+
+	if (wiphy->n_radio < 2)
+		return ret;
+
+	/*
+	 * Multiple HWs are grouped under same wiphy. If not scanning then
+	 * return now itself
+	 */
+	if (!ret)
+		return ret;
+
+	req_radio_idx = cfg80211_get_radio_idx_by_chan(wiphy, chandef->chan);
+	if (req_radio_idx < 0)
+		return true;
+
+	if (local->scanning) {
+		scan_req = wiphy_dereference(wiphy, local->scan_req);
+		/*
+		 * Scan is going on but info is not there. Should not happen
+		 * but if it does, let's not take risk and assume we can't use
+		 * the hw hence return true
+		 */
+		if (WARN_ON_ONCE(!scan_req))
+			return true;
+
+		return ieee80211_is_radio_idx_in_scan_req(wiphy, scan_req,
+							  req_radio_idx);
+	}
+
+	if (!list_empty(&local->roc_list)) {
+		list_for_each_entry(roc, &local->roc_list, list) {
+			chan_radio_idx =
+				cfg80211_get_radio_idx_by_chan(wiphy,
+							       roc->chan);
+			/*
+			 * The roc work is added but chan_radio_idx is invalid.
+			 * Should not happen but if it does, let's not take
+			 * risk and return true.
+			 */
+			if (chan_radio_idx < 0)
+				return true;
+
+			if (chan_radio_idx == req_radio_idx)
+				return true;
+		}
+	}
+
+	return false;
+}
+
 static int ieee80211_start_radar_detection(struct wiphy *wiphy,
 					   struct net_device *dev,
 					   struct cfg80211_chan_def *chandef,
@@ -3562,7 +3624,7 @@ static int ieee80211_start_radar_detection(struct wiphy *wiphy,
 
 	lockdep_assert_wiphy(local->hw.wiphy);
 
-	if (!list_empty(&local->roc_list) || local->scanning)
+	if (__ieee80211_is_scan_ongoing(wiphy, local, chandef))
 		return -EBUSY;
 
 	link_data = sdata_dereference(sdata->link[link_id], sdata);
@@ -4054,7 +4116,7 @@ __ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev,
 
 	lockdep_assert_wiphy(local->hw.wiphy);
 
-	if (!list_empty(&local->roc_list) || local->scanning)
+	if (__ieee80211_is_scan_ongoing(wiphy, local, &params->chandef))
 		return -EBUSY;
 
 	if (sdata->wdev.links[link_id].cac_started)

-- 
2.34.1