mac80211: allow driver to ask for a rate control algorithm

This allows a driver to ask for a specific rate control algorithm.
The rate control algorithm asked for must be registered and be
available as a module or built-in.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -706,11 +706,16 @@ enum ieee80211_hw_flags {
  *
  * @queues: number of available hardware transmit queues for
  *	data packets. WMM/QoS requires at least four.
+ *
+ * @rate_control_algorithm: rate control algorithm for this hardware.
+ *	If unset (NULL), the default algorithm will be used. Must be
+ *	set before calling ieee80211_register_hw().
  */
 struct ieee80211_hw {
 	struct ieee80211_conf conf;
 	struct wiphy *wiphy;
 	struct workqueue_struct *workqueue;
+	const char *rate_control_algorithm;
 	void *priv;
 	u32 flags;
 	unsigned int extra_tx_headroom;

net/mac80211/ieee80211.c

@@ -1072,7 +1072,8 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	ieee80211_debugfs_add_netdev(IEEE80211_DEV_TO_SUB_IF(local->mdev));
 	ieee80211_if_set_type(local->mdev, IEEE80211_IF_TYPE_AP);
 
-	result = ieee80211_init_rate_ctrl_alg(local, NULL);
+	result = ieee80211_init_rate_ctrl_alg(local,
+					      hw->rate_control_algorithm);
 	if (result < 0) {
 		printk(KERN_DEBUG "%s: Failed to initialize rate control "
 		       "algorithm\n", wiphy_name(local->hw.wiphy));