mac80211: allow drivers to request DTIM period

Some features require knowing the DTIM period
before associating. This implements the ability
to wait for a beacon in mac80211 before assoc
to provide this value. It is optional since
most likely not all drivers will need this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -194,7 +194,9 @@ enum ieee80211_bss_change {
  *	if the hardware cannot handle this it must set the
  *	IEEE80211_HW_2GHZ_SHORT_SLOT_INCAPABLE hardware flag
  * @dtim_period: num of beacons before the next DTIM, for beaconing,
- *	not valid in station mode (cf. hw conf ps_dtim_period)
+ *	valid in station mode only while @assoc is true and if also
+ *	requested by %IEEE80211_HW_NEED_DTIM_PERIOD (cf. also hw conf
+ *	@ps_dtim_period)
  * @timestamp: beacon timestamp
  * @beacon_int: beacon interval
  * @assoc_capability: capabilities taken from assoc resp
@@ -1027,6 +1029,9 @@ enum ieee80211_tkip_key_type {
  *	connection quality related parameters, such as the RSSI level and
  *	provide notifications if configured trigger levels are reached.
  *
+ * @IEEE80211_HW_NEED_DTIM_PERIOD:
+ *	This device needs to know the DTIM period for the BSS before
+ *	associating.
  */
 enum ieee80211_hw_flags {
 	IEEE80211_HW_HAS_RATE_CONTROL			= 1<<0,
@@ -1036,7 +1041,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_2GHZ_SHORT_PREAMBLE_INCAPABLE	= 1<<4,
 	IEEE80211_HW_SIGNAL_UNSPEC			= 1<<5,
 	IEEE80211_HW_SIGNAL_DBM				= 1<<6,
-	/* use this hole */
+	IEEE80211_HW_NEED_DTIM_PERIOD			= 1<<7,
 	IEEE80211_HW_SPECTRUM_MGMT			= 1<<8,
 	IEEE80211_HW_AMPDU_AGGREGATION			= 1<<9,
 	IEEE80211_HW_SUPPORTS_PS			= 1<<10,