Your current kernels configuration (.config and linux/autoconf.h)
are always respected when compiling external modules. Because
of this if you are using an old kernel which preferred the
PID rate control algorithm we cannot force it to use minstrel
instead. Minstrel is now the default rate control algorithm
and we want you to use it. To let you use it we redefine here
the CONFIG_MAC80211_RC_DEFAULT to CONFIG_COMPAT_MAC80211_RC_DEFAULT
and define CONFIG_COMPAT_MAC80211_RC_DEFAULT on config.mk.
Through the compat autoconf we then get it also defined there
at compilation time.

--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -24,7 +24,7 @@ struct rate_control_alg {
 static LIST_HEAD(rate_ctrl_algs);
 static DEFINE_MUTEX(rate_ctrl_mutex);
 
-static char *ieee80211_default_rc_algo = CONFIG_MAC80211_RC_DEFAULT;
+static char *ieee80211_default_rc_algo = CONFIG_COMPAT_MAC80211_RC_DEFAULT;
 module_param(ieee80211_default_rc_algo, charp, 0644);
 MODULE_PARM_DESC(ieee80211_default_rc_algo,
 		 "Default rate control algorithm for mac80211 to use");
@@ -120,8 +120,8 @@ ieee80211_rate_control_ops_get(const cha
 		ops = ieee80211_try_rate_control_ops_get(ieee80211_default_rc_algo);
 
 	/* try built-in one if specific alg requested but not found */
-	if (!ops && strlen(CONFIG_MAC80211_RC_DEFAULT))
-		ops = ieee80211_try_rate_control_ops_get(CONFIG_MAC80211_RC_DEFAULT);
+	if (!ops && strlen(CONFIG_COMPAT_MAC80211_RC_DEFAULT))
+		ops = ieee80211_try_rate_control_ops_get(CONFIG_COMPAT_MAC80211_RC_DEFAULT);
 	kparam_unblock_sysfs_write(ieee80211_default_rc_algo);
 
 	return ops;