band: Move ht/vht data rate calculation out of ie.c

src/band.c

@@ -20,9 +20,98 @@
  *
  */
 
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <ell/ell.h>
+
 #include "band.h"
 
 void band_free(struct band *band)
 {
 	l_free(band);
 }
+
+/*
+ * Base RSSI values for 20MHz (both HT and VHT) channel. These values can be
+ * used to calculate the minimum RSSI values for all other channel widths. HT
+ * MCS indexes are grouped into ranges of 8 (per spatial stream) where VHT are
+ * grouped in chunks of 10. This just means HT will not use the last two
+ * index's of this array.
+ */
+static const int32_t ht_vht_base_rssi[] = {
+	-82, -79, -77, -74, -70, -66, -65, -64, -59, -57
+};
+
+/*
+ * Data Rate for HT/VHT is obtained according to this formula:
+ * Nsd * Nbpscs * R * Nss / (Tdft + Tgi)
+ *
+ * Where Nsd is [52, 108, 234, 468] for 20/40/80/160 Mhz respectively
+ * Nbpscs is [1, 2, 4, 6, 8] for BPSK/QPSK/16QAM/64QAM/256QAM
+ * R is [1/2, 2/3, 3/4, 5/6] depending on the MCS index
+ * Nss is the number of spatial streams
+ * Tdft = 3.2 us
+ * Tgi = Long/Short GI of 0.8/0.4 us
+ *
+ * Short GI rate can be easily obtained by multiplying by (10 / 9)
+ *
+ * The table was pre-computed using the following python snippet:
+ * rfactors = [ 1/2, 1/2, 3/4, 1/2, 3/4, 2/3, 3/4, 5/6, 3/4, 5/6 ]
+ * nbpscs = [1, 2, 2, 4, 4, 6, 6, 6, 8, 8 ]
+ * nsds = [52, 108, 234, 468]
+ *
+ * for nsd in nsds:
+ * 	rates = []
+ * 	for i in xrange(0, 10):
+ * 		data_rate = (nsd * rfactors[i] * nbpscs[i]) / 0.004
+ * 		rates.append(int(data_rate) * 1000)
+ * 	print('rates for nsd: ' + nsd + ': ' + rates)
+ */
+
+static const uint64_t ht_vht_rates[4][10] = {
+	[OFDM_CHANNEL_WIDTH_20MHZ] = {
+		6500000ULL, 13000000ULL, 19500000ULL, 26000000ULL,
+		39000000ULL, 52000000ULL, 58500000ULL, 65000000ULL,
+		78000000ULL, 86666000ULL },
+	[OFDM_CHANNEL_WIDTH_40MHZ] = {
+		13500000ULL, 27000000ULL, 40500000ULL, 54000000ULL,
+		81000000ULL, 108000000ULL, 121500000ULL, 135000000ULL,
+		162000000ULL, 180000000ULL, },
+	[OFDM_CHANNEL_WIDTH_80MHZ] = {
+		29250000ULL, 58500000ULL, 87750000ULL, 117000000ULL,
+		175500000ULL, 234000000ULL, 263250000ULL, 292500000ULL,
+		351000000ULL, 390000000ULL, },
+	[OFDM_CHANNEL_WIDTH_160MHZ] = {
+		58500000ULL, 117000000ULL, 175500000ULL, 234000000ULL,
+		351000000ULL, 468000000ULL, 526500000ULL, 585000000ULL,
+		702000000ULL, 780000000ULL,
+	}
+};
+
+/*
+ * Both HT and VHT rates are calculated in the same fashion. The only difference
+ * is a relative MCS index is used for HT since, for each NSS, the formula
+ * is the same with relative index's. This is why this is called with index % 8
+ * for HT, but not VHT.
+ */
+bool band_ofdm_rate(uint8_t index, enum ofdm_channel_width width,
+			int32_t rssi, uint8_t nss, bool sgi,
+			uint64_t *data_rate)
+{
+	uint64_t rate;
+	int32_t width_adjust = width * 3;
+
+	if (rssi < ht_vht_base_rssi[index] + width_adjust)
+		return false;
+
+	rate = ht_vht_rates[width][index];
+
+	if (sgi)
+		rate = rate / 9 * 10;
+
+	rate *= nss;
+
+	*data_rate = rate;
+	return true;
+}

src/band.h

@@ -20,6 +20,13 @@
  *
  */
 
+enum ofdm_channel_width {
+	OFDM_CHANNEL_WIDTH_20MHZ = 0,
+	OFDM_CHANNEL_WIDTH_40MHZ,
+	OFDM_CHANNEL_WIDTH_80MHZ,
+	OFDM_CHANNEL_WIDTH_160MHZ,
+};
+
 struct band {
 	uint8_t vht_mcs_set[8];
 	uint8_t vht_capabilities[4];
@@ -32,3 +39,7 @@ struct band {
 };
 
 void band_free(struct band *band);
+
+bool band_ofdm_rate(uint8_t index, enum ofdm_channel_width width,
+			int32_t rssi, uint8_t nss, bool sgi,
+			uint64_t *data_rate);

src/ie.c

@@ -31,6 +31,7 @@
 #include "ell/useful.h"
 #include "src/util.h"
 #include "src/crypto.h"
+#include "src/band.h"
 #include "src/ie.h"
 
 const unsigned char ieee_oui[3] = { 0x00, 0x0f, 0xac };
@@ -1726,98 +1727,6 @@ static int ie_parse_supported_rates_from_data(const uint8_t *supp_rates_ie,
 	return 0;
 }
 
-enum ht_vht_channel_width {
-	HT_VHT_CHANNEL_WIDTH_20MHZ = 0,
-	HT_VHT_CHANNEL_WIDTH_40MHZ,
-	HT_VHT_CHANNEL_WIDTH_80MHZ,
-	HT_VHT_CHANNEL_WIDTH_160MHZ,
-};
-
-/*
- * Base RSSI values for 20MHz (both HT and VHT) channel. These values can be
- * used to calculate the minimum RSSI values for all other channel widths. HT
- * MCS indexes are grouped into ranges of 8 (per spatial stream) where VHT are
- * grouped in chunks of 10. This just means HT will not use the last two
- * index's of this array.
- */
-static const int32_t ht_vht_base_rssi[] = {
-	-82, -79, -77, -74, -70, -66, -65, -64, -59, -57
-};
-
-/*
- * Data Rate for HT/VHT is obtained according to this formula:
- * Nsd * Nbpscs * R * Nss / (Tdft + Tgi)
- *
- * Where Nsd is [52, 108, 234, 468] for 20/40/80/160 Mhz respectively
- * Nbpscs is [1, 2, 4, 6, 8] for BPSK/QPSK/16QAM/64QAM/256QAM
- * R is [1/2, 2/3, 3/4, 5/6] depending on the MCS index
- * Nss is the number of spatial streams
- * Tdft = 3.2 us
- * Tgi = Long/Short GI of 0.8/0.4 us
- *
- * Short GI rate can be easily obtained by multiplying by (10 / 9)
- *
- * The table was pre-computed using the following python snippet:
- * rfactors = [ 1/2, 1/2, 3/4, 1/2, 3/4, 2/3, 3/4, 5/6, 3/4, 5/6 ]
- * nbpscs = [1, 2, 2, 4, 4, 6, 6, 6, 8, 8 ]
- * nsds = [52, 108, 234, 468]
- *
- * for nsd in nsds:
- * 	rates = []
- * 	for i in xrange(0, 10):
- * 		data_rate = (nsd * rfactors[i] * nbpscs[i]) / 0.004
- * 		rates.append(int(data_rate) * 1000)
- * 	print('rates for nsd: ' + nsd + ': ' + rates)
- */
-
-static const uint64_t ht_vht_rates[4][10] = {
-	[HT_VHT_CHANNEL_WIDTH_20MHZ] = {
-		6500000ULL, 13000000ULL, 19500000ULL, 26000000ULL,
-		39000000ULL, 52000000ULL, 58500000ULL, 65000000ULL,
-		78000000ULL, 86666000ULL },
-	[HT_VHT_CHANNEL_WIDTH_40MHZ] = {
-		13500000ULL, 27000000ULL, 40500000ULL, 54000000ULL,
-		81000000ULL, 108000000ULL, 121500000ULL, 135000000ULL,
-		162000000ULL, 180000000ULL, },
-	[HT_VHT_CHANNEL_WIDTH_80MHZ] = {
-		29250000ULL, 58500000ULL, 87750000ULL, 117000000ULL,
-		175500000ULL, 234000000ULL, 263250000ULL, 292500000ULL,
-		351000000ULL, 390000000ULL, },
-	[HT_VHT_CHANNEL_WIDTH_160MHZ] = {
-		58500000ULL, 117000000ULL, 175500000ULL, 234000000ULL,
-		351000000ULL, 468000000ULL, 526500000ULL, 585000000ULL,
-		702000000ULL, 780000000ULL,
-	}
-};
-
-/*
- * Both HT and VHT rates are calculated in the same fashion. The only difference
- * is a relative MCS index is used for HT since, for each NSS, the formula
- * is the same with relative index's. This is why this is called with index % 8
- * for HT, but not VHT.
- */
-static bool calculate_ht_vht_data_rate(uint8_t index,
-					enum ht_vht_channel_width width,
-					int32_t rssi, uint8_t nss, bool sgi,
-					uint64_t *data_rate)
-{
-	uint64_t rate;
-	int32_t width_adjust = width * 3;
-
-	if (rssi < ht_vht_base_rssi[index] + width_adjust)
-		return false;
-
-	rate = ht_vht_rates[width][index];
-
-	if (sgi)
-		rate = rate / 9 * 10;
-
-	rate *= nss;
-
-	*data_rate = rate;
-	return true;
-}
-
 static int ie_parse_ht_capability(struct ie_tlv_iter *iter, int32_t rssi,
 				uint64_t *data_rate)
 {
@@ -1867,19 +1776,15 @@ static int ie_parse_ht_capability(struct ie_tlv_iter *iter, int32_t rssi,
 		if (!support_40mhz)
 			goto check_20;
 
-		if (calculate_ht_vht_data_rate(i % 8,
+		if (band_ofdm_rate(i % 8, OFDM_CHANNEL_WIDTH_40MHZ,
-						HT_VHT_CHANNEL_WIDTH_40MHZ,
+				rssi, (i / 8) + 1, short_gi_40mhz, &drate)) {
-						rssi, (i / 8) + 1,
-						short_gi_40mhz, &drate)) {
 			*data_rate = drate;
 			return 0;
 		}
 
 check_20:
-		if (!calculate_ht_vht_data_rate(i % 8,
+		if (!band_ofdm_rate(i % 8, OFDM_CHANNEL_WIDTH_20MHZ,
-						HT_VHT_CHANNEL_WIDTH_20MHZ,
+				rssi, (i / 8) + 1, short_gi_20mhz, &drate))
-						rssi, (i / 8) + 1,
-						short_gi_20mhz, &drate))
 			continue;
 
 		if (!support_40mhz) {
@@ -2046,31 +1951,31 @@ static int ie_parse_vht_capability(struct ie_tlv_iter *vht_iter,
 		 * on the channel width for this iteration.
 		 */
 		switch (width) {
-		case HT_VHT_CHANNEL_WIDTH_20MHZ:
+		case OFDM_CHANNEL_WIDTH_20MHZ:
 			sgi = short_gi_20mhz;
 			break;
-		case HT_VHT_CHANNEL_WIDTH_40MHZ:
+		case OFDM_CHANNEL_WIDTH_40MHZ:
 			sgi = short_gi_40mhz;
 			break;
-		case HT_VHT_CHANNEL_WIDTH_80MHZ:
+		case OFDM_CHANNEL_WIDTH_80MHZ:
 			sgi = short_gi_80mhz;
 			break;
-		case HT_VHT_CHANNEL_WIDTH_160MHZ:
+		case OFDM_CHANNEL_WIDTH_160MHZ:
 			sgi = short_gi_160mhz;
 			break;
 		}
 
 		for (nss = minsize(rx_nss, tx_nss); nss > 0; nss--) {
 			/* NSS > 4 does not apply to 20/40MHz */
-			if (width <= HT_VHT_CHANNEL_WIDTH_40MHZ && nss > 4)
+			if (width <= OFDM_CHANNEL_WIDTH_40MHZ && nss > 4)
 				continue;
 
 			for (mcs = minsize(max_rx_mcs, max_tx_mcs);
 						mcs >= 0; mcs--) {
 				uint64_t drate;
 
-				if (!calculate_ht_vht_data_rate(mcs, width,
+				if (!band_ofdm_rate(mcs, width, rssi,
-							rssi, nss, sgi, &drate))
+							nss, sgi, &drate))
 					continue;
 
 				if (drate > highest_rate)