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>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 2aff490..538d6b7 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1737,6 +1737,12 @@
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
*
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 8116d1a..0d2d948 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -515,6 +515,8 @@
* and we need some headroom for passing the frame to monitor
* interfaces, but never both at the same time.
*/
+ BUILD_BUG_ON(IEEE80211_TX_STATUS_HEADROOM !=
+ sizeof(struct ieee80211_tx_status_rtap_hdr));
local->tx_headroom = max_t(unsigned int , local->hw.extra_tx_headroom,
sizeof(struct ieee80211_tx_status_rtap_hdr));