mac80211: implement multi-vif in-place reservations

Multi-vif in-place reservations happen when
it is impossible to allocate more channel contexts
as indicated by interface combinations.

Such reservations are not finalized until all
assigned interfaces are ready.

This still doesn't handle all possible cases
(i.e. degradation of number of channels) properly.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -1606,12 +1606,6 @@ struct ieee80211_tx_control {
  *	is not enabled the default action is to disconnect when getting the
  *	CSA frame.
  *
- * @IEEE80211_HW_CHANGE_RUNNING_CHANCTX: The hardware can change a
- *	channel context on-the-fly.  This is needed for channel switch
- *	on single-channel hardware.  It can also be used as an
- *	optimization in certain channel switch cases with
- *	multi-channel.
- *
  * @IEEE80211_SINGLE_HW_SCAN_ON_ALL_BANDS: The HW supports scanning on all bands
  *	in one command, mac80211 doesn't have to run separate scans per band.
  */
@@ -1645,7 +1639,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_TIMING_BEACON_ONLY			= 1<<26,
 	IEEE80211_HW_SUPPORTS_HT_CCK_RATES		= 1<<27,
 	IEEE80211_HW_CHANCTX_STA_CSA			= 1<<28,
-	IEEE80211_HW_CHANGE_RUNNING_CHANCTX		= 1<<29,
+	/* bit 29 unused */
 	IEEE80211_SINGLE_HW_SCAN_ON_ALL_BANDS		= 1<<30,
 };
 

net/mac80211/ieee80211_i.h

@@ -701,6 +701,24 @@ enum ieee80211_chanctx_mode {
 	IEEE80211_CHANCTX_EXCLUSIVE
 };
 
+/**
+ * enum ieee80211_chanctx_replace_state - channel context replacement state
+ *
+ * This is used for channel context in-place reservations that require channel
+ * context switch/swap.
+ *
+ * @IEEE80211_CHANCTX_REPLACE_NONE: no replacement is taking place
+ * @IEEE80211_CHANCTX_WILL_BE_REPLACED: this channel context will be replaced
+ *	by a (not yet registered) channel context pointed by %replace_ctx.
+ * @IEEE80211_CHANCTX_REPLACES_OTHER: this (not yet registered) channel context
+ *	replaces an existing channel context pointed to by %replace_ctx.
+ */
+enum ieee80211_chanctx_replace_state {
+	IEEE80211_CHANCTX_REPLACE_NONE,
+	IEEE80211_CHANCTX_WILL_BE_REPLACED,
+	IEEE80211_CHANCTX_REPLACES_OTHER,
+};
+
 struct ieee80211_chanctx {
 	struct list_head list;
 	struct rcu_head rcu_head;
@@ -708,6 +726,9 @@ struct ieee80211_chanctx {
 	struct list_head assigned_vifs;
 	struct list_head reserved_vifs;
 
+	enum ieee80211_chanctx_replace_state replace_state;
+	struct ieee80211_chanctx *replace_ctx;
+
 	enum ieee80211_chanctx_mode mode;
 	bool driver_present;
 
@@ -778,6 +799,7 @@ struct ieee80211_sub_if_data {
 	struct ieee80211_chanctx *reserved_chanctx;
 	struct cfg80211_chan_def reserved_chandef;
 	bool reserved_radar_required;
+	bool reserved_ready;
 
 	/* used to reconfigure hardware SM PS */
 	struct work_struct recalc_smps;
@@ -1820,9 +1842,9 @@ ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
 			      enum ieee80211_chanctx_mode mode,
 			      bool radar_required);
 int __must_check
-ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
-				   u32 *changed);
+ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata);
 int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata);
+int ieee80211_vif_use_reserved_switch(struct ieee80211_local *local);
 
 int __must_check
 ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,

net/mac80211/util.c

@@ -1698,7 +1698,9 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 	if (local->use_chanctx) {
 		mutex_lock(&local->chanctx_mtx);
 		list_for_each_entry(ctx, &local->chanctx_list, list)
-			WARN_ON(drv_add_chanctx(local, ctx));
+			if (ctx->replace_state !=
+			    IEEE80211_CHANCTX_REPLACES_OTHER)
+				WARN_ON(drv_add_chanctx(local, ctx));
 		mutex_unlock(&local->chanctx_mtx);
 
 		list_for_each_entry(sdata, &local->interfaces, list) {
@@ -2972,6 +2974,8 @@ int ieee80211_check_combinations(struct ieee80211_sub_if_data *sdata,
 		num[iftype] = 1;
 
 	list_for_each_entry(ctx, &local->chanctx_list, list) {
+		if (ctx->replace_state == IEEE80211_CHANCTX_WILL_BE_REPLACED)
+			continue;
 		if (ctx->conf.radar_enabled)
 			radar_detect |= BIT(ctx->conf.def.width);
 		if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) {
@@ -3030,6 +3034,9 @@ int ieee80211_max_num_channels(struct ieee80211_local *local)
 	lockdep_assert_held(&local->chanctx_mtx);
 
 	list_for_each_entry(ctx, &local->chanctx_list, list) {
+		if (ctx->replace_state == IEEE80211_CHANCTX_WILL_BE_REPLACED)
+			continue;
+
 		num_different_channels++;
 
 		if (ctx->conf.radar_enabled)