mac80211: Add define for TX headroom reserved by mac80211 itself.

Add a definition of the amount of TX headroom reserved by mac80211 itself
for its own purposes. Also add BUILD_BUG_ON to validate the value.
This define can then be used by drivers to request additional TX headroom
in the most efficient manner.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 2aff4906b2ae..538d6b761887 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1737,6 +1737,12 @@ static inline void ieee80211_rx_ni(struct ieee80211_hw *hw,
         local_bh_enable();
 }
 
+/*
+ * The TX headroom reserved by mac80211 for its own tx_status functions.
+ * This is enough for the radiotap header.
+ */
+#define IEEE80211_TX_STATUS_HEADROOM    13
+
 /**
  * ieee80211_tx_status - transmit status callback
  *