ath9k: Fix hanlding of maximum magnitude index

Maximum magnitude index is a 5bit signed integer,
convert to an 8bit signed integer and then "shift" it so that it can be used
as an array index. Note that the current implementation adds +1 to the index
value (so it can't be used as an array index) and it's only valid for HT20
channels.

Note that the maximum magnitude index is not being used by
the userspace tools that parse FFT samples (they just use
maximum magnitude) so this doesn't break userspace compatibility.

Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

diff --git a/drivers/net/wireless/ath/ath9k/common-spectral.c b/drivers/net/wireless/ath/ath9k/common-spectral.c
index 5cee231cca1f99510e21410e362a1086cae19672..8752634d007d8eb6c6e8811474774002e2236bc2 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/common-spectral.c
+++ b/drivers/net/wireless/ath/ath9k/common-spectral.c
@@ -160,8 +160,10 @@ int ath_cmn_process_fft(struct ath_spec_scan_priv *spec_priv, struct ieee80211_h
                upper_mag = spectral_max_magnitude(mag_info->upper_bins);
                fft_sample_40.lower_max_magnitude = __cpu_to_be16(lower_mag);
                fft_sample_40.upper_max_magnitude = __cpu_to_be16(upper_mag);
-               lower_max_index = spectral_max_index(mag_info->lower_bins);
-               upper_max_index = spectral_max_index(mag_info->upper_bins);
+               lower_max_index = spectral_max_index(mag_info->lower_bins,
+                                                               num_bins);
+               upper_max_index = spectral_max_index(mag_info->upper_bins,
+                                                               num_bins);
                fft_sample_40.lower_max_index = lower_max_index;
                fft_sample_40.upper_max_index = upper_max_index;
                lower_bitmap_w = spectral_bitmap_weight(mag_info->lower_bins);
@@ -189,7 +191,8 @@ int ath_cmn_process_fft(struct ath_spec_scan_priv *spec_priv, struct ieee80211_h
                mag_info = ((struct ath_ht20_mag_info *)radar_info) - 1;
                magnitude = spectral_max_magnitude(mag_info->all_bins);
                fft_sample_20.max_magnitude = __cpu_to_be16(magnitude);
-               max_index = spectral_max_index(mag_info->all_bins);
+               max_index = spectral_max_index(mag_info->all_bins,
+                                                       num_bins);
                fft_sample_20.max_index = max_index;
                bitmap_w = spectral_bitmap_weight(mag_info->all_bins);
                fft_sample_20.bitmap_weight = bitmap_w;

diff --git a/drivers/net/wireless/ath/ath9k/common-spectral.h b/drivers/net/wireless/ath/ath9k/common-spectral.h
index 82d9dd29652cd2912239ff51246bdc7f24e6b8a8..072ff76c358108692b806b75354516a173603c7d 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/common-spectral.h
+++ b/drivers/net/wireless/ath/ath9k/common-spectral.h
@@ -111,17 +111,32 @@ static inline u16 spectral_max_magnitude(u8 *bins)
 }
 
 /* return the max magnitude from the all/upper/lower bins */
-static inline u8 spectral_max_index(u8 *bins)
+static inline u8 spectral_max_index(u8 *bins, int num_bins)
 {
        s8 m = (bins[2] & 0xfc) >> 2;
-
-       /* TODO: this still doesn't always report the right values ... */
-       if (m > 32)
+       u8 zero_idx = num_bins / 2;
+
+       /* It's a 5 bit signed int, remove its sign and use one's
+        * complement interpretation to add the sign back to the 8
+        * bit int
+        */
+       if (m & 0x20) {
+               m &= ~0x20;
                m |= 0xe0;
-       else
-               m &= ~0xe0;
+       }
+
+       /* Bring the zero point to the beginning
+        * instead of the middle so that we can use
+        * it for array lookup and that we don't deal
+        * with negative values later
+        */
+       m += zero_idx;
+
+       /* Sanity check to make sure index is within bounds */
+       if (m < 0 || m > num_bins - 1)
+               m = 0;
 
-       return m + 29;
+       return m;
 }
 
 /* return the bitmap weight from the all/upper/lower bins */