mac80211: distinct between max rates and the number of rates the hw can report

Some drivers cannot handle multiple retry rates specified by the rc
algorithm but instead use their own retry table (for example rt2800).
However, if such a device registers itself with a max_rates value of 1
the rc algorithm cannot make use of the extended information the device
can provide about retried rates. On the other hand, if a device
registers itself with a max_rates value > 1 the rc algorithm assumes
that the device can handle multi rate retries.

Fix this issue by introducing another hw parameter max_report_rates that
can be set to a different value then max_rates to indicate if a device
is capable of reporting more rates then specified in max_rates.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -1109,7 +1109,10 @@ enum ieee80211_hw_flags {
  * @sta_data_size: size (in bytes) of the drv_priv data area
  *	within &struct ieee80211_sta.
  *
- * @max_rates: maximum number of alternate rate retry stages
+ * @max_rates: maximum number of alternate rate retry stages the hw
+ *	can handle.
+ * @max_report_rates: maximum number of alternate rate retry stages
+ *	the hw can report back.
  * @max_rate_tries: maximum number of tries for each stage
  *
  * @napi_weight: weight used for NAPI polling.  You must specify an
@@ -1131,6 +1134,7 @@ struct ieee80211_hw {
 	u16 max_listen_interval;
 	s8 max_signal;
 	u8 max_rates;
+	u8 max_report_rates;
 	u8 max_rate_tries;
 };
 

net/mac80211/main.c

@@ -537,6 +537,7 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
 	/* set up some defaults */
 	local->hw.queues = 1;
 	local->hw.max_rates = 1;
+	local->hw.max_report_rates = 0;
 	local->hw.conf.long_frame_max_tx_count = wiphy->retry_long;
 	local->hw.conf.short_frame_max_tx_count = wiphy->retry_short;
 	local->user_power_level = -1;
@@ -612,6 +613,9 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 		WLAN_CIPHER_SUITE_AES_CMAC
 	};
 
+	if (hw->max_report_rates == 0)
+		hw->max_report_rates = hw->max_rates;
+
 	/*
 	 * generic code guarantees at least one band,
 	 * set this very early because much code assumes

net/mac80211/status.c

@@ -176,7 +176,7 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
 
 	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
 		/* the HW cannot have attempted that rate */
-		if (i >= hw->max_rates) {
+		if (i >= hw->max_report_rates) {
 			info->status.rates[i].idx = -1;
 			info->status.rates[i].count = 0;
 		} else if (info->status.rates[i].idx >= 0) {