mac80211: introduce channel context skeleton code

Channel context are the foundation for multi-channel
operation. They are are immutable and are re-created
(or re-used if other interfaces are bound to a certain
channel and a compatible channel type) on channel
switching.

This is an initial implementation and more features
will come in separate patches.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
[some changes including RCU protection]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 82558c8..ab1b5ba 100644 (file)
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -144,6 +144,32 @@ struct ieee80211_low_level_stats {
 };
 
 /**
+ * enum ieee80211_chanctx_change - change flag for channel context
+ * @IEEE80211_CHANCTX_CHANGE_CHANNEL_TYPE: The channel type was changed
+ */
+enum ieee80211_chanctx_change {
+       IEEE80211_CHANCTX_CHANGE_CHANNEL_TYPE   = BIT(0),
+};
+
+/**
+ * struct ieee80211_chanctx_conf - channel context that vifs may be tuned to
+ *
+ * This is the driver-visible part. The ieee80211_chanctx
+ * that contains it is visible in mac80211 only.
+ *
+ * @channel: the channel to tune to
+ * @channel_type: the channel (HT) type
+ * @drv_priv: data area for driver use, will always be aligned to
+ *     sizeof(void *), size is determined in hw information.
+ */
+struct ieee80211_chanctx_conf {
+       struct ieee80211_channel *channel;
+       enum nl80211_channel_type channel_type;
+
+       u8 drv_priv[0] __attribute__((__aligned__(sizeof(void *))));
+};
+
+/**
  * enum ieee80211_bss_change - BSS change notification flags
  *
  * These flags are used with the bss_info_changed() callback
@@ -931,6 +957,11 @@ enum ieee80211_vif_flags {
  *     at runtime, mac80211 will never touch this field
  * @hw_queue: hardware queue for each AC
  * @cab_queue: content-after-beacon (DTIM beacon really) queue, AP mode only
+ * @chanctx_conf: The channel context this interface is assigned to, or %NULL
+ *     when it is not assigned. This pointer is RCU-protected due to the TX
+ *     path needing to access it; even though the netdev carrier will always
+ *     be off when it is %NULL there can still be races and packets could be
+ *     processed after it switches back to %NULL.
  * @drv_priv: data area for driver use, will always be aligned to
  *     sizeof(void *).
  */
@@ -943,6 +974,8 @@ struct ieee80211_vif {
        u8 cab_queue;
        u8 hw_queue[IEEE80211_NUM_ACS];
 
+       struct ieee80211_chanctx_conf __rcu *chanctx_conf;
+
        u32 driver_flags;
 
        /* must be last */
@@ -1325,6 +1358,8 @@ enum ieee80211_hw_flags {
  *     within &struct ieee80211_vif.
  * @sta_data_size: size (in bytes) of the drv_priv data area
  *     within &struct ieee80211_sta.
+ * @chanctx_data_size: size (in bytes) of the drv_priv data area
+ *     within &struct ieee80211_chanctx_conf.
  *
  * @max_rates: maximum number of alternate rate retry stages the hw
  *     can handle.
@@ -1369,6 +1404,7 @@ struct ieee80211_hw {
        int channel_change_time;
        int vif_data_size;
        int sta_data_size;
+       int chanctx_data_size;
        int napi_weight;
        u16 queues;
        u16 max_listen_interval;

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 0bfc914..4ae9486 100644 (file)
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -168,3 +168,150 @@ bool ieee80211_set_channel_type(struct ieee80211_local *local,
        return true;
 
 }
+
+static struct ieee80211_chanctx *
+ieee80211_find_chanctx(struct ieee80211_local *local,
+                      struct ieee80211_channel *channel,
+                      enum nl80211_channel_type channel_type,
+                      enum ieee80211_chanctx_mode mode)
+{
+       struct ieee80211_chanctx *ctx;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       if (mode == IEEE80211_CHANCTX_EXCLUSIVE)
+               return NULL;
+       if (WARN_ON(!channel))
+               return NULL;
+
+       list_for_each_entry(ctx, &local->chanctx_list, list) {
+               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
+                       continue;
+               if (ctx->conf.channel != channel)
+                       continue;
+               if (ctx->conf.channel_type != channel_type)
+                       continue;
+
+               return ctx;
+       }
+
+       return NULL;
+}
+
+static struct ieee80211_chanctx *
+ieee80211_new_chanctx(struct ieee80211_local *local,
+                     struct ieee80211_channel *channel,
+                     enum nl80211_channel_type channel_type,
+                     enum ieee80211_chanctx_mode mode)
+{
+       struct ieee80211_chanctx *ctx;
+
+       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.channel = channel;
+       ctx->conf.channel_type = channel_type;
+       ctx->mode = mode;
+
+       list_add(&ctx->list, &local->chanctx_list);
+
+       return ctx;
+}
+
+static void ieee80211_free_chanctx(struct ieee80211_local *local,
+                                  struct ieee80211_chanctx *ctx)
+{
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       WARN_ON_ONCE(ctx->refcount != 0);
+
+       list_del(&ctx->list);
+       kfree_rcu(ctx, rcu_head);
+}
+
+static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
+                                       struct ieee80211_chanctx *ctx)
+{
+       struct ieee80211_local *local __maybe_unused = sdata->local;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       rcu_assign_pointer(sdata->vif.chanctx_conf, &ctx->conf);
+       ctx->refcount++;
+
+       return 0;
+}
+
+static void ieee80211_unassign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
+                                          struct ieee80211_chanctx *ctx)
+{
+       struct ieee80211_local *local __maybe_unused = sdata->local;
+
+       lockdep_assert_held(&local->chanctx_mtx);
+
+       ctx->refcount--;
+       rcu_assign_pointer(sdata->vif.chanctx_conf, NULL);
+}
+
+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);
+}
+
+int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
+                             struct ieee80211_channel *channel,
+                             enum nl80211_channel_type channel_type,
+                             enum ieee80211_chanctx_mode mode)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx *ctx;
+       int ret;
+
+       mutex_lock(&local->chanctx_mtx);
+       __ieee80211_vif_release_channel(sdata);
+
+       ctx = ieee80211_find_chanctx(local, channel, channel_type, mode);
+       if (!ctx)
+               ctx = ieee80211_new_chanctx(local, channel, channel_type, mode);
+       if (IS_ERR(ctx)) {
+               ret = PTR_ERR(ctx);
+               goto out;
+       }
+
+       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;
+       }
+
+ out:
+       mutex_unlock(&local->chanctx_mtx);
+       return ret;
+}
+
+void ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
+{
+       mutex_lock(&sdata->local->chanctx_mtx);
+       __ieee80211_vif_release_channel(sdata);
+       mutex_unlock(&sdata->local->chanctx_mtx);
+}

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8c80455..9a058e5 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -658,6 +658,30 @@ enum ieee80211_sdata_state_bits {
        SDATA_STATE_OFFCHANNEL,
 };
 
+/**
+ * enum ieee80211_chanctx_mode - channel context configuration mode
+ *
+ * @IEEE80211_CHANCTX_SHARED: channel context may be used by
+ *     multiple interfaces
+ * @IEEE80211_CHANCTX_EXCLUSIVE: channel context can be used
+ *     only by a single interface. This can be used for example for
+ *     non-fixed channel IBSS.
+ */
+enum ieee80211_chanctx_mode {
+       IEEE80211_CHANCTX_SHARED,
+       IEEE80211_CHANCTX_EXCLUSIVE
+};
+
+struct ieee80211_chanctx {
+       struct list_head list;
+       struct rcu_head rcu_head;
+
+       enum ieee80211_chanctx_mode mode;
+       int refcount;
+
+       struct ieee80211_chanctx_conf conf;
+};
+
 struct ieee80211_sub_if_data {
        struct list_head list;
 
@@ -987,6 +1011,10 @@ struct ieee80211_local {
        struct ieee80211_channel *tmp_channel;
        enum nl80211_channel_type tmp_channel_type;
 
+       /* channel contexts */
+       struct list_head chanctx_list;
+       struct mutex chanctx_mtx;
+
        /* SNMP counters */
        /* dot11CountersTable */
        u32 dot11TransmittedFragmentCount;
@@ -1510,6 +1538,13 @@ bool ieee80211_set_channel_type(struct ieee80211_local *local,
 enum nl80211_channel_type
 ieee80211_ht_oper_to_channel_type(struct ieee80211_ht_operation *ht_oper);
 
+int __must_check
+ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
+                         struct ieee80211_channel *channel,
+                         enum nl80211_channel_type channel_type,
+                         enum ieee80211_chanctx_mode mode);
+void ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata);
+
 #ifdef CONFIG_MAC80211_NOINLINE
 #define debug_noinline noinline
 #else

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index c80c449..9be3ef1 100644 (file)
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -626,6 +626,9 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
        spin_lock_init(&local->filter_lock);
        spin_lock_init(&local->queue_stop_reason_lock);
 
+       INIT_LIST_HEAD(&local->chanctx_list);
+       mutex_init(&local->chanctx_mtx);
+
        /*
         * The rx_skb_queue is only accessed from tasklets,
         * but other SKB queues are used from within IRQ