[PATCH v4 1/3] mac80211: add STBC flag for radiotap

[Oleksij Rempel <linux@rempel-privat.de>]

Some chips can tell us if received frame was
encoded with STBC or not. To make this information available
in user space we can use updated radiotap specification:
http://www.radiotap.org/defined-fields/MCS

This patch will set number of STBC encoded spatial streams (Nss).
The HAVE_STBC flag should be provided by driver.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
---
 include/net/ieee80211_radiotap.h | 7 +++++++
 include/net/mac80211.h           | 4 ++++
 net/mac80211/rx.c                | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/include/net/ieee80211_radiotap.h b/include/net/ieee80211_radiotap.h
index c399963..c6d07cb 100644
--- a/include/net/ieee80211_radiotap.h
+++ b/include/net/ieee80211_radiotap.h
@@ -269,6 +269,7 @@ enum ieee80211_radiotap_type {
 #define IEEE80211_RADIOTAP_MCS_HAVE_GI		0x04
 #define IEEE80211_RADIOTAP_MCS_HAVE_FMT		0x08
 #define IEEE80211_RADIOTAP_MCS_HAVE_FEC		0x10
+#define IEEE80211_RADIOTAP_MCS_HAVE_STBC	0x20
 
 #define IEEE80211_RADIOTAP_MCS_BW_MASK		0x03
 #define		IEEE80211_RADIOTAP_MCS_BW_20	0
@@ -278,6 +279,12 @@ enum ieee80211_radiotap_type {
 #define IEEE80211_RADIOTAP_MCS_SGI		0x04
 #define IEEE80211_RADIOTAP_MCS_FMT_GF		0x08
 #define IEEE80211_RADIOTAP_MCS_FEC_LDPC		0x10
+#define IEEE80211_RADIOTAP_MCS_STBC_MASK	0x60
+#define		IEEE80211_RADIOTAP_MCS_STBC_1	1
+#define		IEEE80211_RADIOTAP_MCS_STBC_2	2
+#define		IEEE80211_RADIOTAP_MCS_STBC_3	3
+
+#define IEEE80211_RADIOTAP_MCS_STBC_SHIFT	5
 
 /* For IEEE80211_RADIOTAP_AMPDU_STATUS */
 #define IEEE80211_RADIOTAP_AMPDU_REPORT_ZEROLEN		0x0001
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 885898a..16705a9 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -805,6 +805,7 @@ ieee80211_tx_info_clear_status(struct ieee80211_tx_info *info)
  *	on this subframe
  * @RX_FLAG_AMPDU_DELIM_CRC_KNOWN: The delimiter CRC field is known (the CRC
  *	is stored in the @ampdu_delimiter_crc field)
+ * @RX_FLAG_STBC_MASK: STBC 2 bit bitmask. 1 - Nss=1, 2 - Nss=2, 3 - Nss=3
  */
 enum mac80211_rx_flags {
 	RX_FLAG_MMIC_ERROR		= BIT(0),
@@ -832,8 +833,11 @@ enum mac80211_rx_flags {
 	RX_FLAG_80MHZ			= BIT(23),
 	RX_FLAG_80P80MHZ		= BIT(24),
 	RX_FLAG_160MHZ			= BIT(25),
+	RX_FLAG_STBC_MASK		= BIT(26) | BIT(27),
 };
 
+#define RX_FLAG_STBC_SHIFT		26
+
 /**
  * struct ieee80211_rx_status - receive status
  *
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 8e29526..811dd64 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -258,6 +258,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 	pos += 2;
 
 	if (status->flag & RX_FLAG_HT) {
+		unsigned int stbc;
 		rthdr->it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_MCS);
 		*pos++ = local->hw.radiotap_mcs_details;
 		*pos = 0;
@@ -267,6 +268,9 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 			*pos |= IEEE80211_RADIOTAP_MCS_BW_40;
 		if (status->flag & RX_FLAG_HT_GF)
 			*pos |= IEEE80211_RADIOTAP_MCS_FMT_GF;
+		stbc = status->flag & RX_FLAG_STBC_MASK;
+		*pos |= (stbc >> RX_FLAG_STBC_SHIFT)
+				<< IEEE80211_RADIOTAP_MCS_STBC_SHIFT;
 		pos++;
 		*pos++ = status->rate_idx;
 	}
-- 
1.8.1.2