ieee80211: add new VHT capability fields/parsing

IEEE 802.11-2016 extended the VHT capability fields to allow
indicating the number of spatial streams depending on the
actually used bandwidth, add support for decoding this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 109 insertions, 0 deletions

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 4293f980e9c4..ef14d80ca03e 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -5,17 +5,20 @@
  * Copyright 2007-2009	Johannes Berg <johannes@sipsolutions.net>
  * Copyright 2013-2014  Intel Mobile Communications GmbH
  * Copyright 2017	Intel Deutschland GmbH
+ * Copyright (C) 2018 Intel Corporation
  */
 #include <linux/export.h>
 #include <linux/bitops.h>
 #include <linux/etherdevice.h>
 #include <linux/slab.h>
+#include <linux/ieee80211.h>
 #include <net/cfg80211.h>
 #include <net/ip.h>
 #include <net/dsfield.h>
 #include <linux/if_vlan.h>
 #include <linux/mpls.h>
 #include <linux/gcd.h>
+#include <linux/bitfield.h>
 #include "core.h"
 #include "rdev-ops.h"
 
@@ -1938,3 +1941,109 @@ void cfg80211_send_layer2_update(struct net_device *dev, const u8 *addr)
 	netif_rx_ni(skb);
 }
 EXPORT_SYMBOL(cfg80211_send_layer2_update);
+
+int ieee80211_get_vht_max_nss(struct ieee80211_vht_cap *cap,
+			      enum ieee80211_vht_chanwidth bw,
+			      int mcs, bool ext_nss_bw_capable)
+{
+	u16 map = le16_to_cpu(cap->supp_mcs.rx_mcs_map);
+	int max_vht_nss = 0;
+	int ext_nss_bw;
+	int supp_width;
+	int i, mcs_encoding;
+
+	if (map == 0xffff)
+		return 0;
+
+	if (WARN_ON(mcs > 9))
+		return 0;
+	if (mcs <= 7)
+		mcs_encoding = 0;
+	else if (mcs == 8)
+		mcs_encoding = 1;
+	else
+		mcs_encoding = 2;
+
+	/* find max_vht_nss for the given MCS */
+	for (i = 7; i >= 0; i--) {
+		int supp = (map >> (2 * i)) & 3;
+
+		if (supp == 3)
+			continue;
+
+		if (supp >= mcs_encoding) {
+			max_vht_nss = i;
+			break;
+		}
+	}
+
+	if (!(cap->supp_mcs.tx_mcs_map &
+			cpu_to_le16(IEEE80211_VHT_EXT_NSS_BW_CAPABLE)))
+		return max_vht_nss;
+
+	ext_nss_bw = le32_get_bits(cap->vht_cap_info,
+				   IEEE80211_VHT_CAP_EXT_NSS_BW_MASK);
+	supp_width = le32_get_bits(cap->vht_cap_info,
+				   IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK);
+
+	/* if not capable, treat ext_nss_bw as 0 */
+	if (!ext_nss_bw_capable)
+		ext_nss_bw = 0;
+
+	/* This is invalid */
+	if (supp_width == 3)
+		return 0;
+
+	/* This is an invalid combination so pretend nothing is supported */
+	if (supp_width == 2 && (ext_nss_bw == 1 || ext_nss_bw == 2))
+		return 0;
+
+	/*
+	 * Cover all the special cases according to IEEE 802.11-2016
+	 * Table 9-250. All other cases are either factor of 1 or not
+	 * valid/supported.
+	 */
+	switch (bw) {
+	case IEEE80211_VHT_CHANWIDTH_USE_HT:
+	case IEEE80211_VHT_CHANWIDTH_80MHZ:
+		if ((supp_width == 1 || supp_width == 2) &&
+		    ext_nss_bw == 3)
+			return 2 * max_vht_nss;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_160MHZ:
+		if (supp_width == 0 &&
+		    (ext_nss_bw == 1 || ext_nss_bw == 2))
+			return DIV_ROUND_UP(max_vht_nss, 2);
+		if (supp_width == 0 &&
+		    ext_nss_bw == 3)
+			return DIV_ROUND_UP(3 * max_vht_nss, 4);
+		if (supp_width == 1 &&
+		    ext_nss_bw == 3)
+			return 2 * max_vht_nss;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_80P80MHZ:
+		if (supp_width == 0 &&
+		    (ext_nss_bw == 1 || ext_nss_bw == 2))
+			return 0; /* not possible */
+		if (supp_width == 0 &&
+		    ext_nss_bw == 2)
+			return DIV_ROUND_UP(max_vht_nss, 2);
+		if (supp_width == 0 &&
+		    ext_nss_bw == 3)
+			return DIV_ROUND_UP(3 * max_vht_nss, 4);
+		if (supp_width == 1 &&
+		    ext_nss_bw == 0)
+			return 0; /* not possible */
+		if (supp_width == 1 &&
+		    ext_nss_bw == 1)
+			return DIV_ROUND_UP(max_vht_nss, 2);
+		if (supp_width == 1 &&
+		    ext_nss_bw == 2)
+			return DIV_ROUND_UP(3 * max_vht_nss, 4);
+		break;
+	}
+
+	/* not covered or invalid combination received */
+	return max_vht_nss;
+}
+EXPORT_SYMBOL(ieee80211_get_vht_max_nss);