/*
   * mac80211 - channel management
   */
  
  #include <linux/nl80211.h>
  #include <linux/export.h>
  #include <linux/rtnetlink.h>
  #include <net/cfg80211.h>
  #include "ieee80211_i.h"
  #include "driver-ops.h"
  
  static enum nl80211_chan_width ieee80211_get_sta_bw(struct ieee80211_sta *sta)
  {
  	switch (sta->bandwidth) {
  	case IEEE80211_STA_RX_BW_20:
  		if (sta->ht_cap.ht_supported)
  			return NL80211_CHAN_WIDTH_20;
  		else
  			return NL80211_CHAN_WIDTH_20_NOHT;
  	case IEEE80211_STA_RX_BW_40:
  		return NL80211_CHAN_WIDTH_40;
  	case IEEE80211_STA_RX_BW_80:
  		return NL80211_CHAN_WIDTH_80;
  	case IEEE80211_STA_RX_BW_160:
  		/*
  		 * This applied for both 160 and 80+80. since we use
  		 * the returned value to consider degradation of
  		 * ctx->conf.min_def, we have to make sure to take
  		 * the bigger one (NL80211_CHAN_WIDTH_160).
  		 * Otherwise we might try degrading even when not
  		 * needed, as the max required sta_bw returned (80+80)
  		 * might be smaller than the configured bw (160).
  		 */
  		return NL80211_CHAN_WIDTH_160;
  	default:
  		WARN_ON(1);
  		return NL80211_CHAN_WIDTH_20;
  	}
  }
  
  static enum nl80211_chan_width
  ieee80211_get_max_required_bw(struct ieee80211_sub_if_data *sdata)
  {
  	enum nl80211_chan_width max_bw = NL80211_CHAN_WIDTH_20_NOHT;
  	struct sta_info *sta;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(sta, &sdata->local->sta_list, list) {
  		if (sdata != sta->sdata &&
  		    !(sta->sdata->bss && sta->sdata->bss == sdata->bss))
  			continue;
  
  		if (!sta->uploaded)
  			continue;
  
  		max_bw = max(max_bw, ieee80211_get_sta_bw(&sta->sta));
  	}
  	rcu_read_unlock();
  
  	return max_bw;
  }
  
  static enum nl80211_chan_width
  ieee80211_get_chanctx_max_required_bw(struct ieee80211_local *local,
  				      struct ieee80211_chanctx_conf *conf)
  {
  	struct ieee80211_sub_if_data *sdata;
  	enum nl80211_chan_width max_bw = NL80211_CHAN_WIDTH_20_NOHT;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
  		struct ieee80211_vif *vif = &sdata->vif;
  		enum nl80211_chan_width width = NL80211_CHAN_WIDTH_20_NOHT;
  
  		if (!ieee80211_sdata_running(sdata))
  			continue;
  
  		if (rcu_access_pointer(sdata->vif.chanctx_conf) != conf)
  			continue;
  
  		switch (vif->type) {
  		case NL80211_IFTYPE_AP:
  		case NL80211_IFTYPE_AP_VLAN:
  			width = ieee80211_get_max_required_bw(sdata);
  			break;
  		case NL80211_IFTYPE_P2P_DEVICE:
  			continue;
  		case NL80211_IFTYPE_STATION:
  		case NL80211_IFTYPE_ADHOC:
  		case NL80211_IFTYPE_WDS:
  		case NL80211_IFTYPE_MESH_POINT:
  			width = vif->bss_conf.chandef.width;
  			break;
  		case NL80211_IFTYPE_UNSPECIFIED:
  		case NUM_NL80211_IFTYPES:
  		case NL80211_IFTYPE_MONITOR:
  		case NL80211_IFTYPE_P2P_CLIENT:
  		case NL80211_IFTYPE_P2P_GO:
  			WARN_ON_ONCE(1);
  		}
  		max_bw = max(max_bw, width);
  	}
  
  	/* use the configured bandwidth in case of monitor interface */
  	sdata = rcu_dereference(local->monitor_sdata);
  	if (sdata && rcu_access_pointer(sdata->vif.chanctx_conf) == conf)
  		max_bw = max(max_bw, conf->def.width);
  
  	rcu_read_unlock();
  
  	return max_bw;
  }
  
  /*
   * recalc the min required chan width of the channel context, which is
   * the max of min required widths of all the interfaces bound to this
   * channel context.
   */
  void ieee80211_recalc_chanctx_min_def(struct ieee80211_local *local,
  				      struct ieee80211_chanctx *ctx)
  {
  	enum nl80211_chan_width max_bw;
  	struct cfg80211_chan_def min_def;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	/* don't optimize 5MHz, 10MHz, and radar_enabled confs */
  	if (ctx->conf.def.width == NL80211_CHAN_WIDTH_5 ||
  	    ctx->conf.def.width == NL80211_CHAN_WIDTH_10 ||
  	    ctx->conf.radar_enabled) {
  		ctx->conf.min_def = ctx->conf.def;
  		return;
  	}
  
  	max_bw = ieee80211_get_chanctx_max_required_bw(local, &ctx->conf);
  
  	/* downgrade chandef up to max_bw */
  	min_def = ctx->conf.def;
  	while (min_def.width > max_bw)
  		ieee80211_chandef_downgrade(&min_def);
  
  	if (cfg80211_chandef_identical(&ctx->conf.min_def, &min_def))
  		return;
  
  	ctx->conf.min_def = min_def;
  	if (!ctx->driver_present)
  		return;
  
  	drv_change_chanctx(local, ctx, IEEE80211_CHANCTX_CHANGE_MIN_WIDTH);
  }
  
  static void ieee80211_change_chanctx(struct ieee80211_local *local,
  				     struct ieee80211_chanctx *ctx,
  				     const struct cfg80211_chan_def *chandef)
  {
  	if (cfg80211_chandef_identical(&ctx->conf.def, chandef))
  		return;
  
  	WARN_ON(!cfg80211_chandef_compatible(&ctx->conf.def, chandef));
  
  	ctx->conf.def = *chandef;
  	drv_change_chanctx(local, ctx, IEEE80211_CHANCTX_CHANGE_WIDTH);
  	ieee80211_recalc_chanctx_min_def(local, ctx);
  
  	if (!local->use_chanctx) {
  		local->_oper_chandef = *chandef;
  		ieee80211_hw_config(local, 0);
  	}
  }
  
  static struct ieee80211_chanctx *
  ieee80211_find_chanctx(struct ieee80211_local *local,
  		       const struct cfg80211_chan_def *chandef,
  		       enum ieee80211_chanctx_mode mode)
  {
  	struct ieee80211_chanctx *ctx;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	if (mode == IEEE80211_CHANCTX_EXCLUSIVE)
  		return NULL;
  
  	list_for_each_entry(ctx, &local->chanctx_list, list) {
  		const struct cfg80211_chan_def *compat;
  
  		if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
  			continue;
  
  		compat = cfg80211_chandef_compatible(&ctx->conf.def, chandef);
  		if (!compat)
  			continue;
  
  		ieee80211_change_chanctx(local, ctx, compat);
  
  		return ctx;
  	}
  
  	return NULL;
  }
  
  static bool ieee80211_is_radar_required(struct ieee80211_local *local)
  {
  	struct ieee80211_sub_if_data *sdata;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
  		if (sdata->radar_required) {
  			rcu_read_unlock();
  			return true;
  		}
  	}
  	rcu_read_unlock();
  
  	return false;
  }
  
  static struct ieee80211_chanctx *
  ieee80211_new_chanctx(struct ieee80211_local *local,
  		      const struct cfg80211_chan_def *chandef,
  		      enum ieee80211_chanctx_mode mode)
  {
  	struct ieee80211_chanctx *ctx;
  	u32 changed;
  	int err;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	ctx = kzalloc(sizeof(*ctx) + local->hw.chanctx_data_size, GFP_KERNEL);
  	if (!ctx)
  		return ERR_PTR(-ENOMEM);
  
  	ctx->conf.def = *chandef;
  	ctx->conf.rx_chains_static = 1;
  	ctx->conf.rx_chains_dynamic = 1;
  	ctx->mode = mode;
  	ctx->conf.radar_enabled = ieee80211_is_radar_required(local);
  	ieee80211_recalc_chanctx_min_def(local, ctx);
  	if (!local->use_chanctx)
  		local->hw.conf.radar_enabled = ctx->conf.radar_enabled;
  
  	/* we hold the mutex to prevent idle from changing */
  	lockdep_assert_held(&local->mtx);
  	/* turn idle off *before* setting channel -- some drivers need that */
  	changed = ieee80211_idle_off(local);
  	if (changed)
  		ieee80211_hw_config(local, changed);
  
  	if (!local->use_chanctx) {
  		local->_oper_chandef = *chandef;
  		ieee80211_hw_config(local, 0);
  	} else {
  		err = drv_add_chanctx(local, ctx);
  		if (err) {
  			kfree(ctx);
  			ieee80211_recalc_idle(local);
  			return ERR_PTR(err);
  		}
  	}
  
  	/* and keep the mutex held until the new chanctx is on the list */
  	list_add_rcu(&ctx->list, &local->chanctx_list);
  
  	return ctx;
  }
  
  static void ieee80211_free_chanctx(struct ieee80211_local *local,
  				   struct ieee80211_chanctx *ctx)
  {
  	bool check_single_channel = false;
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	WARN_ON_ONCE(ctx->refcount != 0);
  
  	if (!local->use_chanctx) {
  		struct cfg80211_chan_def *chandef = &local->_oper_chandef;
  		chandef->width = NL80211_CHAN_WIDTH_20_NOHT;
  		chandef->center_freq1 = chandef->chan->center_freq;
  		chandef->center_freq2 = 0;
  
  		/* NOTE: Disabling radar is only valid here for
  		 * single channel context. To be sure, check it ...
  		 */
  		if (local->hw.conf.radar_enabled)
  			check_single_channel = true;
  		local->hw.conf.radar_enabled = false;
  
  		ieee80211_hw_config(local, 0);
  	} else {
  		drv_remove_chanctx(local, ctx);
  	}
  
  	list_del_rcu(&ctx->list);
  	kfree_rcu(ctx, rcu_head);
  
  	/* throw a warning if this wasn't the only channel context. */
  	WARN_ON(check_single_channel && !list_empty(&local->chanctx_list));
  
  	ieee80211_recalc_idle(local);
  }
  
  static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
  					struct ieee80211_chanctx *ctx)
  {
  	struct ieee80211_local *local = sdata->local;
  	int ret;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	ret = drv_assign_vif_chanctx(local, sdata, ctx);
  	if (ret)
  		return ret;
  
  	rcu_assign_pointer(sdata->vif.chanctx_conf, &ctx->conf);
  	ctx->refcount++;
  
  	ieee80211_recalc_txpower(sdata);
  	ieee80211_recalc_chanctx_min_def(local, ctx);
  	sdata->vif.bss_conf.idle = false;
  
  	if (sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
  	    sdata->vif.type != NL80211_IFTYPE_MONITOR)
  		ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_IDLE);
  
  	return 0;
  }
  
  static void ieee80211_recalc_chanctx_chantype(struct ieee80211_local *local,
  					      struct ieee80211_chanctx *ctx)
  {
  	struct ieee80211_chanctx_conf *conf = &ctx->conf;
  	struct ieee80211_sub_if_data *sdata;
  	const struct cfg80211_chan_def *compat = NULL;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
  
  		if (!ieee80211_sdata_running(sdata))
  			continue;
  		if (rcu_access_pointer(sdata->vif.chanctx_conf) != conf)
  			continue;
  
  		if (!compat)
  			compat = &sdata->vif.bss_conf.chandef;
  
  		compat = cfg80211_chandef_compatible(
  				&sdata->vif.bss_conf.chandef, compat);
  		if (!compat)
  			break;
  	}
  	rcu_read_unlock();
  
  	if (WARN_ON_ONCE(!compat))
  		return;
  
  	ieee80211_change_chanctx(local, ctx, compat);
  }
  
  static void ieee80211_recalc_radar_chanctx(struct ieee80211_local *local,
  					   struct ieee80211_chanctx *chanctx)
  {
  	bool radar_enabled;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  	/* for setting local->radar_detect_enabled */
  	lockdep_assert_held(&local->mtx);
  
  	radar_enabled = ieee80211_is_radar_required(local);
  
  	if (radar_enabled == chanctx->conf.radar_enabled)
  		return;
  
  	chanctx->conf.radar_enabled = radar_enabled;
  	local->radar_detect_enabled = chanctx->conf.radar_enabled;
  
  	if (!local->use_chanctx) {
  		local->hw.conf.radar_enabled = chanctx->conf.radar_enabled;
  		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
  	}
  
  	drv_change_chanctx(local, chanctx, IEEE80211_CHANCTX_CHANGE_RADAR);
  }
  
  static void ieee80211_unassign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
  					   struct ieee80211_chanctx *ctx)
  {
  	struct ieee80211_local *local = sdata->local;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	ctx->refcount--;
  	rcu_assign_pointer(sdata->vif.chanctx_conf, NULL);
  
  	sdata->vif.bss_conf.idle = true;
  
  	if (sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
  	    sdata->vif.type != NL80211_IFTYPE_MONITOR)
  		ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_IDLE);
  
  	drv_unassign_vif_chanctx(local, sdata, ctx);
  
  	if (ctx->refcount > 0) {
  		ieee80211_recalc_chanctx_chantype(sdata->local, ctx);
  		ieee80211_recalc_smps_chanctx(local, ctx);
  		ieee80211_recalc_radar_chanctx(local, ctx);
  		ieee80211_recalc_chanctx_min_def(local, ctx);
  	}
  }
  
  static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_chanctx_conf *conf;
  	struct ieee80211_chanctx *ctx;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
  					 lockdep_is_held(&local->chanctx_mtx));
  	if (!conf)
  		return;
  
  	ctx = container_of(conf, struct ieee80211_chanctx, conf);
  
  	ieee80211_unassign_vif_chanctx(sdata, ctx);
  	if (ctx->refcount == 0)
  		ieee80211_free_chanctx(local, ctx);
  }
  
  void ieee80211_recalc_smps_chanctx(struct ieee80211_local *local,
  				   struct ieee80211_chanctx *chanctx)
  {
  	struct ieee80211_sub_if_data *sdata;
  	u8 rx_chains_static, rx_chains_dynamic;
  
  	lockdep_assert_held(&local->chanctx_mtx);
  
  	rx_chains_static = 1;
  	rx_chains_dynamic = 1;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
  		u8 needed_static, needed_dynamic;
  
  		if (!ieee80211_sdata_running(sdata))
  			continue;
  
  		if (rcu_access_pointer(sdata->vif.chanctx_conf) !=
  						&chanctx->conf)
  			continue;
  
  		switch (sdata->vif.type) {
  		case NL80211_IFTYPE_P2P_DEVICE:
  			continue;
  		case NL80211_IFTYPE_STATION:
  			if (!sdata->u.mgd.associated)
  				continue;
  			break;
  		case NL80211_IFTYPE_AP_VLAN:
  			continue;
  		case NL80211_IFTYPE_AP:
  		case NL80211_IFTYPE_ADHOC:
  		case NL80211_IFTYPE_WDS:
  		case NL80211_IFTYPE_MESH_POINT:
  			break;
  		default:
  			WARN_ON_ONCE(1);
  		}
  
  		switch (sdata->smps_mode) {
  		default:
  			WARN_ONCE(1, "Invalid SMPS mode %d
  ",
  				  sdata->smps_mode);
  			/* fall through */
  		case IEEE80211_SMPS_OFF:
  			needed_static = sdata->needed_rx_chains;
  			needed_dynamic = sdata->needed_rx_chains;
  			break;
  		case IEEE80211_SMPS_DYNAMIC:
  			needed_static = 1;
  			needed_dynamic = sdata->needed_rx_chains;
  			break;
  		case IEEE80211_SMPS_STATIC:
  			needed_static = 1;
  			needed_dynamic = 1;
  			break;
  		}
  
  		rx_chains_static = max(rx_chains_static, needed_static);
  		rx_chains_dynamic = max(rx_chains_dynamic, needed_dynamic);
  	}
  	rcu_read_unlock();
  
  	if (!local->use_chanctx) {
  		if (rx_chains_static > 1)
  			local->smps_mode = IEEE80211_SMPS_OFF;
  		else if (rx_chains_dynamic > 1)
  			local->smps_mode = IEEE80211_SMPS_DYNAMIC;
  		else
  			local->smps_mode = IEEE80211_SMPS_STATIC;
  		ieee80211_hw_config(local, 0);
  	}
  
  	if (rx_chains_static == chanctx->conf.rx_chains_static &&
  	    rx_chains_dynamic == chanctx->conf.rx_chains_dynamic)
  		return;
  
  	chanctx->conf.rx_chains_static = rx_chains_static;
  	chanctx->conf.rx_chains_dynamic = rx_chains_dynamic;
  	drv_change_chanctx(local, chanctx, IEEE80211_CHANCTX_CHANGE_RX_CHAINS);
  }
  
  int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
  			      const struct cfg80211_chan_def *chandef,
  			      enum ieee80211_chanctx_mode mode)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_chanctx *ctx;
  	int ret;
  
  	lockdep_assert_held(&local->mtx);
  
  	WARN_ON(sdata->dev && netif_carrier_ok(sdata->dev));
  
  	mutex_lock(&local->chanctx_mtx);
  	__ieee80211_vif_release_channel(sdata);
  
  	ctx = ieee80211_find_chanctx(local, chandef, mode);
  	if (!ctx)
  		ctx = ieee80211_new_chanctx(local, chandef, mode);
  	if (IS_ERR(ctx)) {
  		ret = PTR_ERR(ctx);
  		goto out;
  	}
  
  	sdata->vif.bss_conf.chandef = *chandef;
  
  	ret = ieee80211_assign_vif_chanctx(sdata, ctx);
  	if (ret) {
  		/* if assign fails refcount stays the same */
  		if (ctx->refcount == 0)
  			ieee80211_free_chanctx(local, ctx);
  		goto out;
  	}
  
  	ieee80211_recalc_smps_chanctx(local, ctx);
  	ieee80211_recalc_radar_chanctx(local, ctx);
   out:
  	mutex_unlock(&local->chanctx_mtx);
  	return ret;
  }
  
  int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
  				 u32 *changed)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_chanctx_conf *conf;
  	struct ieee80211_chanctx *ctx;
  	const struct cfg80211_chan_def *chandef = &sdata->csa_chandef;
  	int ret;
  	u32 chanctx_changed = 0;
  
  	lockdep_assert_held(&local->mtx);
  
  	/* should never be called if not performing a channel switch. */
  	if (WARN_ON(!sdata->vif.csa_active))
  		return -EINVAL;
  
  	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
  				     IEEE80211_CHAN_DISABLED))
  		return -EINVAL;
  
  	mutex_lock(&local->chanctx_mtx);
  	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
  					 lockdep_is_held(&local->chanctx_mtx));
  	if (!conf) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	ctx = container_of(conf, struct ieee80211_chanctx, conf);
  	if (ctx->refcount != 1) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	if (sdata->vif.bss_conf.chandef.width != chandef->width) {
  		chanctx_changed = IEEE80211_CHANCTX_CHANGE_WIDTH;
  		*changed |= BSS_CHANGED_BANDWIDTH;
  	}
  
  	sdata->vif.bss_conf.chandef = *chandef;
  	ctx->conf.def = *chandef;
  
  	chanctx_changed |= IEEE80211_CHANCTX_CHANGE_CHANNEL;
  	drv_change_chanctx(local, ctx, chanctx_changed);
  
  	ieee80211_recalc_chanctx_chantype(local, ctx);
  	ieee80211_recalc_smps_chanctx(local, ctx);
  	ieee80211_recalc_radar_chanctx(local, ctx);
  	ieee80211_recalc_chanctx_min_def(local, ctx);
  
  	ret = 0;
   out:
  	mutex_unlock(&local->chanctx_mtx);
  	return ret;
  }
  
  int ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
  				   const struct cfg80211_chan_def *chandef,
  				   u32 *changed)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_chanctx_conf *conf;
  	struct ieee80211_chanctx *ctx;
  	int ret;
  
  	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
  				     IEEE80211_CHAN_DISABLED))
  		return -EINVAL;
  
  	mutex_lock(&local->chanctx_mtx);
  	if (cfg80211_chandef_identical(chandef, &sdata->vif.bss_conf.chandef)) {
  		ret = 0;
  		goto out;
  	}
  
  	if (chandef->width == NL80211_CHAN_WIDTH_20_NOHT ||
  	    sdata->vif.bss_conf.chandef.width == NL80211_CHAN_WIDTH_20_NOHT) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
  					 lockdep_is_held(&local->chanctx_mtx));
  	if (!conf) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	ctx = container_of(conf, struct ieee80211_chanctx, conf);
  	if (!cfg80211_chandef_compatible(&conf->def, chandef)) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	sdata->vif.bss_conf.chandef = *chandef;
  
  	ieee80211_recalc_chanctx_chantype(local, ctx);
  
  	*changed |= BSS_CHANGED_BANDWIDTH;
  	ret = 0;
   out:
  	mutex_unlock(&local->chanctx_mtx);
  	return ret;
  }
  
  void ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
  {
  	WARN_ON(sdata->dev && netif_carrier_ok(sdata->dev));
  
  	lockdep_assert_held(&sdata->local->mtx);
  
  	mutex_lock(&sdata->local->chanctx_mtx);
  	__ieee80211_vif_release_channel(sdata);
  	mutex_unlock(&sdata->local->chanctx_mtx);
  }
  
  void ieee80211_vif_vlan_copy_chanctx(struct ieee80211_sub_if_data *sdata)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_sub_if_data *ap;
  	struct ieee80211_chanctx_conf *conf;
  
  	if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP_VLAN || !sdata->bss))
  		return;
  
  	ap = container_of(sdata->bss, struct ieee80211_sub_if_data, u.ap);
  
  	mutex_lock(&local->chanctx_mtx);
  
  	conf = rcu_dereference_protected(ap->vif.chanctx_conf,
  					 lockdep_is_held(&local->chanctx_mtx));
  	rcu_assign_pointer(sdata->vif.chanctx_conf, conf);
  	mutex_unlock(&local->chanctx_mtx);
  }
  
  void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
  					 bool clear)
  {
  	struct ieee80211_local *local = sdata->local;
  	struct ieee80211_sub_if_data *vlan;
  	struct ieee80211_chanctx_conf *conf;
  
  	ASSERT_RTNL();
  
  	if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP))
  		return;
  
  	mutex_lock(&local->chanctx_mtx);
  
  	/*
  	 * Check that conf exists, even when clearing this function
  	 * must be called with the AP's channel context still there
  	 * as it would otherwise cause VLANs to have an invalid
  	 * channel context pointer for a while, possibly pointing
  	 * to a channel context that has already been freed.
  	 */
  	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
  				lockdep_is_held(&local->chanctx_mtx));
  	WARN_ON(!conf);
  
  	if (clear)
  		conf = NULL;
  
  	list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
  		rcu_assign_pointer(vlan->vif.chanctx_conf, conf);
  
  	mutex_unlock(&local->chanctx_mtx);
  }
  
  void ieee80211_iter_chan_contexts_atomic(
  	struct ieee80211_hw *hw,
  	void (*iter)(struct ieee80211_hw *hw,
  		     struct ieee80211_chanctx_conf *chanctx_conf,
  		     void *data),
  	void *iter_data)
  {
  	struct ieee80211_local *local = hw_to_local(hw);
  	struct ieee80211_chanctx *ctx;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(ctx, &local->chanctx_list, list)
  		if (ctx->driver_present)
  			iter(hw, &ctx->conf, iter_data);
  	rcu_read_unlock();
  }
  EXPORT_SYMBOL_GPL(ieee80211_iter_chan_contexts_atomic);