mac80211: Add new callback set_coverage_class

Mac80211 callback to driver set_coverage_class() sets slot time and ACK
timeout for given IEEE 802.11 coverage class. The callback is optional,
but it's essential for long distance links.

Signed-off-by: Lukas Turek <8an@praha12.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index f073a2a..ad4b700 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1533,6 +1533,10 @@
  *	and need to call wiphy_rfkill_set_hw_state() in the callback.
  *	The callback can sleep.
  *
+ * @set_coverage_class: Set slot time for given coverage class as specified
+ *	in IEEE 802.11-2007 section 17.3.8.6 and modify ACK timeout
+ *	accordingly. This callback is not required and may sleep.
+ *
  * @testmode_cmd: Implement a cfg80211 test mode command.
  *	The callback can sleep.
  *
@@ -1592,6 +1596,7 @@
 			    struct ieee80211_sta *sta, u16 tid, u16 *ssn);
 
 	void (*rfkill_poll)(struct ieee80211_hw *hw);
+	void (*set_coverage_class)(struct ieee80211_hw *hw, u8 coverage_class);
 #ifdef CONFIG_NL80211_TESTMODE
 	int (*testmode_cmd)(struct ieee80211_hw *hw, void *data, int len);
 #endif