mac80211: parse the HT capabilities info through debugfs

When debugging you want to be lazy and not have to parse
bits yourself so let mac80211 debugfs do the parsing for you.

This is what I get against my WRT610N:

root@tux:~# cat /sys/kernel/debug/ieee80211/phy0/stations/00\:22\:6b\:aa\:bb\:01/ht_capa
ht supported
cap: 0x000e
	HT20/HT40
	SM Power Save disabled
	No RX STBC
	Max AMSDU length: 7935 bytes
	No DSSS/CCK HT40
ampdu factor/density: 2/6
MCS mask: ff ff 00 00 00 00 00 00 00 00
MCS rx highest: 0
MCS tx params: 0

Cc: johannes@sipsolutions.net
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/debugfs_sta.c

@@ -160,7 +160,12 @@ STA_OPS(agg_status);
 static ssize_t sta_ht_capa_read(struct file *file, char __user *userbuf,
 				size_t count, loff_t *ppos)
 {
-	char buf[200], *p = buf;
+#define PRINT_HT_CAP(_cond, _str) \
+	do { \
+	if (_cond) \
+			p += scnprintf(p, sizeof(buf)+buf-p, "\t" _str "\n"); \
+	} while (0)
+	char buf[1024], *p = buf;
 	int i;
 	struct sta_info *sta = file->private_data;
 	struct ieee80211_sta_ht_cap *htc = &sta->sta.ht_cap;
@@ -169,6 +174,47 @@ static ssize_t sta_ht_capa_read(struct file *file, char __user *userbuf,
 			htc->ht_supported ? "" : "not ");
 	if (htc->ht_supported) {
 		p += scnprintf(p, sizeof(buf)+buf-p, "cap: %#.4x\n", htc->cap);
+
+		PRINT_HT_CAP((htc->cap & BIT(0)), "RX LDCP");
+		PRINT_HT_CAP((htc->cap & BIT(1)), "HT20/HT40");
+		PRINT_HT_CAP(!(htc->cap & BIT(1)), "HT20");
+
+		PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 0, "Static SM Power Save");
+		PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 1, "Dynamic SM Power Save");
+		PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 3, "SM Power Save disabled");
+
+		PRINT_HT_CAP((htc->cap & BIT(4)), "RX Greenfield");
+		PRINT_HT_CAP((htc->cap & BIT(5)), "RX HT20 SGI");
+		PRINT_HT_CAP((htc->cap & BIT(6)), "RX HT40 SGI");
+		PRINT_HT_CAP((htc->cap & BIT(7)), "TX STBC");
+
+		PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 0, "No RX STBC");
+		PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 1, "RX STBC 1-stream");
+		PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 2, "RX STBC 2-streams");
+		PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 3, "RX STBC 3-streams");
+
+		PRINT_HT_CAP((htc->cap & BIT(10)), "HT Delayed Block Ack");
+
+		PRINT_HT_CAP((htc->cap & BIT(11)), "Max AMSDU length: "
+			     "3839 bytes");
+		PRINT_HT_CAP(!(htc->cap & BIT(11)), "Max AMSDU length: "
+			     "7935 bytes");
+
+		/*
+		 * For beacons and probe response this would mean the BSS
+		 * does or does not allow the usage of DSSS/CCK HT40.
+		 * Otherwise it means the STA does or does not use
+		 * DSSS/CCK HT40.
+		 */
+		PRINT_HT_CAP((htc->cap & BIT(12)), "DSSS/CCK HT40");
+		PRINT_HT_CAP(!(htc->cap & BIT(12)), "No DSSS/CCK HT40");
+
+		/* BIT(13) is reserved */
+
+		PRINT_HT_CAP((htc->cap & BIT(14)), "40 MHz Intolerant");
+
+		PRINT_HT_CAP((htc->cap & BIT(15)), "L-SIG TXOP protection");
+
 		p += scnprintf(p, sizeof(buf)+buf-p, "ampdu factor/density: %d/%d\n",
 				htc->ampdu_factor, htc->ampdu_density);
 		p += scnprintf(p, sizeof(buf)+buf-p, "MCS mask:");