wireless: report reasonable bitrate for MCS rates through wext

Previously, cfg80211 had reported "0" for MCS (i.e. 802.11n) bitrates
through the wireless extensions interface.  However, nl80211 was
converting MCS rates into a reasonable bitrate number.  This patch moves
the nl80211 code to cfg80211 where it is now shared between both the
nl80211 interface and the wireless extensions interface.

Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 59361fdcb5d0..a3c841a255db 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -720,3 +720,36 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 
         return err;
 }
+
+u16 cfg80211_calculate_bitrate(struct rate_info *rate)
+{
+        int modulation, streams, bitrate;
+
+        if (!(rate->flags & RATE_INFO_FLAGS_MCS))
+                return rate->legacy;
+
+        /* the formula below does only work for MCS values smaller than 32 */
+        if (rate->mcs >= 32)
+                return 0;
+
+        modulation = rate->mcs & 7;
+        streams = (rate->mcs >> 3) + 1;
+
+        bitrate = (rate->flags & RATE_INFO_FLAGS_40_MHZ_WIDTH) ?
+                        13500000 : 6500000;
+
+        if (modulation < 4)
+                bitrate *= (modulation + 1);
+        else if (modulation == 4)
+                bitrate *= (modulation + 2);
+        else
+                bitrate *= (modulation + 3);
+
+        bitrate *= streams;
+
+        if (rate->flags & RATE_INFO_FLAGS_SHORT_GI)
+                bitrate = (bitrate / 9) * 10;
+
+        /* do NOT round down here */
+        return (bitrate + 50000) / 100000;
+}