]> git.kernelconcepts.de Git - karo-tx-linux.git/blobdiff - net/mac80211/chan.c
Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[karo-tx-linux.git] / net / mac80211 / chan.c
index 75b5dd2c9267f10e8cb0e5680c3aa11c94a5dbe4..a310e33972de8881bf4dd71bdff36d55fa966226 100644 (file)
@@ -9,6 +9,170 @@
 #include "ieee80211_i.h"
 #include "driver-ops.h"
 
+static int ieee80211_chanctx_num_assigned(struct ieee80211_local *local,
+                                         struct ieee80211_chanctx *ctx)
+{
+       struct ieee80211_sub_if_data *sdata;
+       int num = 0;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       list_for_each_entry(sdata, &ctx->assigned_vifs, assigned_chanctx_list)
+               num++;
+
+       return num;
+}
+
+static int ieee80211_chanctx_num_reserved(struct ieee80211_local *local,
+                                         struct ieee80211_chanctx *ctx)
+{
+       struct ieee80211_sub_if_data *sdata;
+       int num = 0;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       list_for_each_entry(sdata, &ctx->reserved_vifs, reserved_chanctx_list)
+               num++;
+
+       return num;
+}
+
+int ieee80211_chanctx_refcount(struct ieee80211_local *local,
+                              struct ieee80211_chanctx *ctx)
+{
+       return ieee80211_chanctx_num_assigned(local, ctx) +
+              ieee80211_chanctx_num_reserved(local, ctx);
+}
+
+static int ieee80211_num_chanctx(struct ieee80211_local *local)
+{
+       struct ieee80211_chanctx *ctx;
+       int num = 0;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       list_for_each_entry(ctx, &local->chanctx_list, list)
+               num++;
+
+       return num;
+}
+
+static bool ieee80211_can_create_new_chanctx(struct ieee80211_local *local)
+{
+       lockdep_assert_held(&local->chanctx_mtx);
+       return ieee80211_num_chanctx(local) < ieee80211_max_num_channels(local);
+}
+
+static const struct cfg80211_chan_def *
+ieee80211_chanctx_reserved_chandef(struct ieee80211_local *local,
+                                  struct ieee80211_chanctx *ctx,
+                                  const struct cfg80211_chan_def *compat)
+{
+       struct ieee80211_sub_if_data *sdata;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       list_for_each_entry(sdata, &ctx->reserved_vifs,
+                           reserved_chanctx_list) {
+               if (!compat)
+                       compat = &sdata->reserved_chandef;
+
+               compat = cfg80211_chandef_compatible(&sdata->reserved_chandef,
+                                                    compat);
+               if (!compat)
+                       break;
+       }
+
+       return compat;
+}
+
+static const struct cfg80211_chan_def *
+ieee80211_chanctx_non_reserved_chandef(struct ieee80211_local *local,
+                                      struct ieee80211_chanctx *ctx,
+                                      const struct cfg80211_chan_def *compat)
+{
+       struct ieee80211_sub_if_data *sdata;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       list_for_each_entry(sdata, &ctx->assigned_vifs,
+                           assigned_chanctx_list) {
+               if (sdata->reserved_chanctx != NULL)
+                       continue;
+
+               if (!compat)
+                       compat = &sdata->vif.bss_conf.chandef;
+
+               compat = cfg80211_chandef_compatible(
+                               &sdata->vif.bss_conf.chandef, compat);
+               if (!compat)
+                       break;
+       }
+
+       return compat;
+}
+
+static const struct cfg80211_chan_def *
+ieee80211_chanctx_combined_chandef(struct ieee80211_local *local,
+                                  struct ieee80211_chanctx *ctx,
+                                  const struct cfg80211_chan_def *compat)
+{
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       compat = ieee80211_chanctx_reserved_chandef(local, ctx, compat);
+       if (!compat)
+               return NULL;
+
+       compat = ieee80211_chanctx_non_reserved_chandef(local, ctx, compat);
+       if (!compat)
+               return NULL;
+
+       return compat;
+}
+
+static bool
+ieee80211_chanctx_can_reserve_chandef(struct ieee80211_local *local,
+                                     struct ieee80211_chanctx *ctx,
+                                     const struct cfg80211_chan_def *def)
+{
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       if (ieee80211_chanctx_combined_chandef(local, ctx, def))
+               return true;
+
+       if (!list_empty(&ctx->reserved_vifs) &&
+           ieee80211_chanctx_reserved_chandef(local, ctx, def))
+               return true;
+
+       return false;
+}
+
+static struct ieee80211_chanctx *
+ieee80211_find_reservation_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) {
+               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
+                       continue;
+
+               if (!ieee80211_chanctx_can_reserve_chandef(local, ctx,
+                                                          chandef))
+                       continue;
+
+               return ctx;
+       }
+
+       return NULL;
+}
+
 static enum nl80211_chan_width ieee80211_get_sta_bw(struct ieee80211_sta *sta)
 {
        switch (sta->bandwidth) {
@@ -190,6 +354,11 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
                if (!compat)
                        continue;
 
+               compat = ieee80211_chanctx_reserved_chandef(local, ctx,
+                                                           compat);
+               if (!compat)
+                       continue;
+
                ieee80211_change_chanctx(local, ctx, compat);
 
                return ctx;
@@ -217,62 +386,91 @@ static bool ieee80211_is_radar_required(struct ieee80211_local *local)
 }
 
 static struct ieee80211_chanctx *
-ieee80211_new_chanctx(struct ieee80211_local *local,
-                     const struct cfg80211_chan_def *chandef,
-                     enum ieee80211_chanctx_mode mode)
+ieee80211_alloc_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);
+               return NULL;
 
+       INIT_LIST_HEAD(&ctx->assigned_vifs);
+       INIT_LIST_HEAD(&ctx->reserved_vifs);
        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);
+
+       return ctx;
+}
+
+static int ieee80211_add_chanctx(struct ieee80211_local *local,
+                                struct ieee80211_chanctx *ctx)
+{
+       u32 changed;
+       int err;
+
+       lockdep_assert_held(&local->mtx);
+       lockdep_assert_held(&local->chanctx_mtx);
+
        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;
+               local->_oper_chandef = ctx->conf.def;
                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
        } else {
                err = drv_add_chanctx(local, ctx);
                if (err) {
-                       kfree(ctx);
                        ieee80211_recalc_idle(local);
-                       return ERR_PTR(err);
+                       return err;
                }
        }
 
-       /* and keep the mutex held until the new chanctx is on the list */
-       list_add_rcu(&ctx->list, &local->chanctx_list);
+       return 0;
+}
 
+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;
+       int err;
+
+       lockdep_assert_held(&local->mtx);
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       ctx = ieee80211_alloc_chanctx(local, chandef, mode);
+       if (!ctx)
+               return ERR_PTR(-ENOMEM);
+
+       err = ieee80211_add_chanctx(local, ctx);
+       if (err) {
+               kfree(ctx);
+               return ERR_PTR(err);
+       }
+
+       list_add_rcu(&ctx->list, &local->chanctx_list);
        return ctx;
 }
 
-static void ieee80211_free_chanctx(struct ieee80211_local *local,
-                                  struct ieee80211_chanctx *ctx)
+static void ieee80211_del_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;
@@ -282,8 +480,9 @@ static void ieee80211_free_chanctx(struct ieee80211_local *local,
                /* 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;
+               WARN_ON(local->hw.conf.radar_enabled &&
+                       !list_empty(&local->chanctx_list));
+
                local->hw.conf.radar_enabled = false;
 
                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
@@ -291,39 +490,19 @@ static void ieee80211_free_chanctx(struct ieee80211_local *local,
                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)
+static void ieee80211_free_chanctx(struct ieee80211_local *local,
+                                  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;
+       WARN_ON_ONCE(ieee80211_chanctx_refcount(local, ctx) != 0);
 
-       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;
+       list_del_rcu(&ctx->list);
+       ieee80211_del_chanctx(local, ctx);
+       kfree_rcu(ctx, rcu_head);
 }
 
 static void ieee80211_recalc_chanctx_chantype(struct ieee80211_local *local,
@@ -384,30 +563,58 @@ static void ieee80211_recalc_radar_chanctx(struct ieee80211_local *local,
        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)
+static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
+                                       struct ieee80211_chanctx *new_ctx)
 {
        struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx_conf *conf;
+       struct ieee80211_chanctx *curr_ctx = NULL;
+       int ret = 0;
 
-       lockdep_assert_held(&local->chanctx_mtx);
+       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+                                        lockdep_is_held(&local->chanctx_mtx));
 
-       ctx->refcount--;
-       rcu_assign_pointer(sdata->vif.chanctx_conf, NULL);
+       if (conf) {
+               curr_ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
-       sdata->vif.bss_conf.idle = true;
+               drv_unassign_vif_chanctx(local, sdata, curr_ctx);
+               conf = NULL;
+               list_del(&sdata->assigned_chanctx_list);
+       }
 
-       if (sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
-           sdata->vif.type != NL80211_IFTYPE_MONITOR)
-               ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_IDLE);
+       if (new_ctx) {
+               ret = drv_assign_vif_chanctx(local, sdata, new_ctx);
+               if (ret)
+                       goto out;
 
-       drv_unassign_vif_chanctx(local, sdata, ctx);
+               conf = &new_ctx->conf;
+               list_add(&sdata->assigned_chanctx_list,
+                        &new_ctx->assigned_vifs);
+       }
+
+out:
+       rcu_assign_pointer(sdata->vif.chanctx_conf, conf);
+
+       sdata->vif.bss_conf.idle = !conf;
+
+       if (curr_ctx && ieee80211_chanctx_num_assigned(local, curr_ctx) > 0) {
+               ieee80211_recalc_chanctx_chantype(local, curr_ctx);
+               ieee80211_recalc_smps_chanctx(local, curr_ctx);
+               ieee80211_recalc_radar_chanctx(local, curr_ctx);
+               ieee80211_recalc_chanctx_min_def(local, curr_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);
+       if (new_ctx && ieee80211_chanctx_num_assigned(local, new_ctx) > 0) {
+               ieee80211_recalc_txpower(sdata);
+               ieee80211_recalc_chanctx_min_def(local, new_ctx);
        }
+
+       if (sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
+           sdata->vif.type != NL80211_IFTYPE_MONITOR)
+               ieee80211_bss_info_change_notify(sdata,
+                                                BSS_CHANGED_IDLE);
+
+       return ret;
 }
 
 static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
@@ -425,8 +632,11 @@ static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
 
        ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
-       ieee80211_unassign_vif_chanctx(sdata, ctx);
-       if (ctx->refcount == 0)
+       if (sdata->reserved_chanctx)
+               ieee80211_vif_unreserve_chanctx(sdata);
+
+       ieee80211_assign_vif_chanctx(sdata, NULL);
+       if (ieee80211_chanctx_refcount(local, ctx) == 0)
                ieee80211_free_chanctx(local, ctx);
 }
 
@@ -526,6 +736,7 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
 {
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_chanctx *ctx;
+       u8 radar_detect_width = 0;
        int ret;
 
        lockdep_assert_held(&local->mtx);
@@ -533,6 +744,22 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
        WARN_ON(sdata->dev && netif_carrier_ok(sdata->dev));
 
        mutex_lock(&local->chanctx_mtx);
+
+       ret = cfg80211_chandef_dfs_required(local->hw.wiphy,
+                                           chandef,
+                                           sdata->wdev.iftype);
+       if (ret < 0)
+               goto out;
+       if (ret > 0)
+               radar_detect_width = BIT(chandef->width);
+
+       sdata->radar_required = ret;
+
+       ret = ieee80211_check_combinations(sdata, chandef, mode,
+                                          radar_detect_width);
+       if (ret < 0)
+               goto out;
+
        __ieee80211_vif_release_channel(sdata);
 
        ctx = ieee80211_find_chanctx(local, chandef, mode);
@@ -548,7 +775,7 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
        ret = ieee80211_assign_vif_chanctx(sdata, ctx);
        if (ret) {
                /* if assign fails refcount stays the same */
-               if (ctx->refcount == 0)
+               if (ieee80211_chanctx_refcount(local, ctx) == 0)
                        ieee80211_free_chanctx(local, ctx);
                goto out;
        }
@@ -560,15 +787,47 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
        return ret;
 }
 
+static int __ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
+                                         struct ieee80211_chanctx *ctx,
+                                         u32 *changed)
+{
+       struct ieee80211_local *local = sdata->local;
+       const struct cfg80211_chan_def *chandef = &sdata->csa_chandef;
+       u32 chanctx_changed = 0;
+
+       if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
+                                    IEEE80211_CHAN_DISABLED))
+               return -EINVAL;
+
+       if (ieee80211_chanctx_refcount(local, ctx) != 1)
+               return -EINVAL;
+
+       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);
+
+       return 0;
+}
+
 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);
 
@@ -576,11 +835,94 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
        if (WARN_ON(!sdata->vif.csa_active))
                return -EINVAL;
 
-       if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
-                                    IEEE80211_CHAN_DISABLED))
+       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);
+
+       ret = __ieee80211_vif_change_channel(sdata, ctx, changed);
+ out:
+       mutex_unlock(&local->chanctx_mtx);
+       return ret;
+}
+
+static void
+__ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
+                                     bool clear)
+{
+       struct ieee80211_local *local __maybe_unused = sdata->local;
+       struct ieee80211_sub_if_data *vlan;
+       struct ieee80211_chanctx_conf *conf;
+
+       if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP))
+               return;
+
+       lockdep_assert_held(&local->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);
+}
+
+void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
+                                        bool clear)
+{
+       struct ieee80211_local *local = sdata->local;
+
+       mutex_lock(&local->chanctx_mtx);
+
+       __ieee80211_vif_copy_chanctx_to_vlans(sdata, clear);
+
+       mutex_unlock(&local->chanctx_mtx);
+}
+
+int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata)
+{
+       struct ieee80211_chanctx *ctx = sdata->reserved_chanctx;
+
+       lockdep_assert_held(&sdata->local->chanctx_mtx);
+
+       if (WARN_ON(!ctx))
                return -EINVAL;
 
+       list_del(&sdata->reserved_chanctx_list);
+       sdata->reserved_chanctx = NULL;
+
+       if (ieee80211_chanctx_refcount(sdata->local, ctx) == 0)
+               ieee80211_free_chanctx(sdata->local, ctx);
+
+       return 0;
+}
+
+int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
+                                 const struct cfg80211_chan_def *chandef,
+                                 enum ieee80211_chanctx_mode mode,
+                                 bool radar_required)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx_conf *conf;
+       struct ieee80211_chanctx *new_ctx, *curr_ctx;
+       int ret = 0;
+
        mutex_lock(&local->chanctx_mtx);
+
        conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
                                         lockdep_is_held(&local->chanctx_mtx));
        if (!conf) {
@@ -588,30 +930,108 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
                goto out;
        }
 
-       ctx = container_of(conf, struct ieee80211_chanctx, conf);
-       if (ctx->refcount != 1) {
+       curr_ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+       new_ctx = ieee80211_find_reservation_chanctx(local, chandef, mode);
+       if (!new_ctx) {
+               if (ieee80211_chanctx_refcount(local, curr_ctx) == 1 &&
+                   (local->hw.flags & IEEE80211_HW_CHANGE_RUNNING_CHANCTX)) {
+                       /* if we're the only users of the chanctx and
+                        * the driver supports changing a running
+                        * context, reserve our current context
+                        */
+                       new_ctx = curr_ctx;
+               } else if (ieee80211_can_create_new_chanctx(local)) {
+                       /* create a new context and reserve it */
+                       new_ctx = ieee80211_new_chanctx(local, chandef, mode);
+                       if (IS_ERR(new_ctx)) {
+                               ret = PTR_ERR(new_ctx);
+                               goto out;
+                       }
+               } else {
+                       ret = -EBUSY;
+                       goto out;
+               }
+       }
+
+       list_add(&sdata->reserved_chanctx_list, &new_ctx->reserved_vifs);
+       sdata->reserved_chanctx = new_ctx;
+       sdata->reserved_chandef = *chandef;
+       sdata->reserved_radar_required = radar_required;
+out:
+       mutex_unlock(&local->chanctx_mtx);
+       return ret;
+}
+
+int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
+                                      u32 *changed)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx *ctx;
+       struct ieee80211_chanctx *old_ctx;
+       struct ieee80211_chanctx_conf *conf;
+       int ret;
+       u32 tmp_changed = *changed;
+
+       /* TODO: need to recheck if the chandef is usable etc.? */
+
+       lockdep_assert_held(&local->mtx);
+
+       mutex_lock(&local->chanctx_mtx);
+
+       ctx = sdata->reserved_chanctx;
+       if (WARN_ON(!ctx)) {
                ret = -EINVAL;
                goto out;
        }
 
-       if (sdata->vif.bss_conf.chandef.width != chandef->width) {
-               chanctx_changed = IEEE80211_CHANCTX_CHANGE_WIDTH;
-               *changed |= BSS_CHANGED_BANDWIDTH;
+       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+                                        lockdep_is_held(&local->chanctx_mtx));
+       if (!conf) {
+               ret = -EINVAL;
+               goto out;
        }
 
-       sdata->vif.bss_conf.chandef = *chandef;
-       ctx->conf.def = *chandef;
+       old_ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
-       chanctx_changed |= IEEE80211_CHANCTX_CHANGE_CHANNEL;
-       drv_change_chanctx(local, ctx, chanctx_changed);
+       if (sdata->vif.bss_conf.chandef.width != sdata->reserved_chandef.width)
+               tmp_changed |= BSS_CHANGED_BANDWIDTH;
+
+       sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
+
+       /* unref our reservation */
+       sdata->reserved_chanctx = NULL;
+       sdata->radar_required = sdata->reserved_radar_required;
+       list_del(&sdata->reserved_chanctx_list);
+
+       if (old_ctx == ctx) {
+               /* This is our own context, just change it */
+               ret = __ieee80211_vif_change_channel(sdata, old_ctx,
+                                                    &tmp_changed);
+               if (ret)
+                       goto out;
+       } else {
+               ret = ieee80211_assign_vif_chanctx(sdata, ctx);
+               if (ieee80211_chanctx_refcount(local, old_ctx) == 0)
+                       ieee80211_free_chanctx(local, old_ctx);
+               if (ret) {
+                       /* if assign fails refcount stays the same */
+                       if (ieee80211_chanctx_refcount(local, ctx) == 0)
+                               ieee80211_free_chanctx(local, ctx);
+                       goto out;
+               }
+
+               if (sdata->vif.type == NL80211_IFTYPE_AP)
+                       __ieee80211_vif_copy_chanctx_to_vlans(sdata, false);
+       }
+
+       *changed = tmp_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:
+out:
        mutex_unlock(&local->chanctx_mtx);
        return ret;
 }
@@ -695,40 +1115,6 @@ void ieee80211_vif_vlan_copy_chanctx(struct ieee80211_sub_if_data *sdata)
        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,