mac80211: add PID controller based rate control algorithm

Add a new rate control algorithm based on a PID controller. It samples the
percentage of failed frames over time, feeds the result into the controller and
uses its output to control the TX rate.
Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mac80211/Kconfig

@@ -25,6 +25,18 @@ config MAC80211_RCSIMPLE
 	  Say Y unless you know you will have another algorithm
 	  available.
 
+config MAC80211_RCPID
+	bool "'PID' rate control algorithm" if EMBEDDED
+	default y
+	depends on MAC80211
+	help
+	  This option enables a TX rate control algorithm for
+	  mac80211 that uses a PID controller to select the TX
+	  rate.
+
+	  Say Y unless you're sure you want to use a different
+	  rate control algorithm.
+
 config MAC80211_LEDS
 	bool "Enable LED triggers"
 	depends on MAC80211 && LEDS_TRIGGERS

net/mac80211/Makefile

@@ -4,6 +4,7 @@ mac80211-objs-$(CONFIG_MAC80211_LEDS) += ieee80211_led.o
 mac80211-objs-$(CONFIG_MAC80211_DEBUGFS) += debugfs.o debugfs_sta.o debugfs_netdev.o debugfs_key.o
 mac80211-objs-$(CONFIG_NET_SCHED) += wme.o
 mac80211-objs-$(CONFIG_MAC80211_RCSIMPLE) += rc80211_simple.o
+mac80211-objs-$(CONFIG_MAC80211_RCPID) += rc80211_pid.o
 
 mac80211-objs := \
 	ieee80211.o \

net/mac80211/ieee80211.c

@@ -1315,23 +1315,37 @@ static int __init ieee80211_init(void)
 #ifdef CONFIG_MAC80211_RCSIMPLE
 	ret = ieee80211_rate_control_register(&mac80211_rcsimple);
 	if (ret)
-		return ret;
+		goto fail;
+#endif
+
+#ifdef CONFIG_MAC80211_RCPID
+	ret = ieee80211_rate_control_register(&mac80211_rcpid);
+	if (ret)
+		goto fail;
 #endif
 
 	ret = ieee80211_wme_register();
 	if (ret) {
-#ifdef CONFIG_MAC80211_RCSIMPLE
-		ieee80211_rate_control_unregister(&mac80211_rcsimple);
-#endif
 		printk(KERN_DEBUG "ieee80211_init: failed to "
 		       "initialize WME (err=%d)\n", ret);
-		return ret;
+		goto fail;
 	}
 
 	ieee80211_debugfs_netdev_init();
 	ieee80211_regdomain_init();
 
 	return 0;
+
+fail:
+
+#ifdef CONFIG_MAC80211_RCSIMPLE
+	ieee80211_rate_control_unregister(&mac80211_rcsimple);
+#endif
+#ifdef CONFIG_MAC80211_RCPID
+	ieee80211_rate_control_unregister(&mac80211_rcpid);
+#endif
+
+	return ret;
 }
 
 static void __exit ieee80211_exit(void)
@@ -1339,6 +1353,9 @@ static void __exit ieee80211_exit(void)
 #ifdef CONFIG_MAC80211_RCSIMPLE
 	ieee80211_rate_control_unregister(&mac80211_rcsimple);
 #endif
+#ifdef CONFIG_MAC80211_RCPID
+	ieee80211_rate_control_unregister(&mac80211_rcpid);
+#endif
 
 	ieee80211_wme_unregister();
 	ieee80211_debugfs_netdev_exit();

net/mac80211/ieee80211_rate.h

@@ -61,6 +61,9 @@ struct rate_control_ref {
 /* default 'simple' algorithm */
 extern struct rate_control_ops mac80211_rcsimple;
 
+/* 'PID' algorithm */
+extern struct rate_control_ops mac80211_rcpid;
+
 int ieee80211_rate_control_register(struct rate_control_ops *ops);
 void ieee80211_rate_control_unregister(struct rate_control_ops *ops);