mcbts: Fix maximum number in channels in multicarrier config

Maximum number of carriers is fixed to 3 channels on a single
physical RF channel.

Fixes: Coverity CID 149353t
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>

Transceiver52M/Resampler.cpp

@@ -185,13 +185,13 @@ int Resampler::rotate(const float *in, size_t in_len, float *out, size_t out_len
 			      n, 1, 1, 0);
 	}
 
-	return out_len;
+	return 0;
 }
 
 bool Resampler::init(float bw)
 {
 	/* Filterbank filter internals */
-	if (initFilters(bw) < 0)
+	if (!initFilters(bw))
 		return false;
 
 	/* Precompute filterbank paths */

Transceiver52M/Resampler.h

@@ -47,7 +47,7 @@ public:
 	 *   @param in_len input buffer length
 	 *   @param out continuous buffer of output complex float values
 	 *   @param out_len output buffer length
-	 *   @return number of samples outputted, negative on error
+	 *   @return 0 on success and negative on error
          *
 	 * Input and output vector lengths must of be equal multiples of the
 	 * rational conversion rate denominator and numerator respectively.

Transceiver52M/osmo-trx.cpp

@@ -43,11 +43,10 @@
 
 /*
  * Samples-per-symbol for uplink (receiver) path
- *     Do not modify this value. EDGE configures 4 sps automatically on
- *     B200/B210 devices only. Use of 4 sps on the receive path for other
- *     configurations is not supported.
+ *     4 - Provides better timing precision (avoids FPGA DDC timing ambiguity)
+ *     1 - Reduces processor load, but increases timing ambiguity
  */
-#define DEFAULT_RX_SPS		1
+#define DEFAULT_RX_SPS		4
 
 /* Default configuration parameters
  *     Note that these values are only used if the particular key does not
@@ -61,6 +60,9 @@
 #define DEFAULT_DIVERSITY	false
 #define DEFAULT_CHANS		1
 
+/* Max number of channels in multi-carrier configuration */
+#define MAX_MCHANS		3
+
 struct trx_config {
 	std::string log_level;
 	std::string addr;
@@ -168,7 +170,7 @@ bool trx_setup_config(struct trx_config *config)
 	if (!config->chans)
 		config->chans = DEFAULT_CHANS;
 
-	if (config->mcbts && ((config->chans < 0) || (config->chans > 5))) {
+	if (config->mcbts && (config->chans > MAX_MCHANS)) {
 		std::cout << "Unsupported number of channels" << std::endl;
 		return false;
 	}

Transceiver52M/sigProcLib.cpp

@@ -1729,8 +1729,10 @@ bool energyDetect(signalVector &rxBurst,
 
   signalVector::const_iterator windowItr = rxBurst.begin(); //+rxBurst.size()/2 - 5*windowLength/2;
   float energy = 0.0;
-  if (windowLength < 0) windowLength = 20;
-  if (windowLength > rxBurst.size()) windowLength = rxBurst.size();
+
+  if (windowLength > rxBurst.size())
+    windowLength = rxBurst.size();
+
   for (unsigned i = 0; i < windowLength; i++) {
     energy += windowItr->norm2();
     windowItr+=4;
@@ -1790,10 +1792,6 @@ static int detectBurst(signalVector &burst,
   /* Normalize our channel gain */
   *amp = *amp / sync->gain;
 
-  /* Compenate for residual rotation with dual Laurent pulse */
-  if (sps == 4)
-    *amp = *amp * complex(0.0, 1.0);
-
   /* Compensate for residuate time lag */
   *toa = *toa - sync->toa;
 
@@ -1911,7 +1909,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
   int rc, target, head, tail;
   CorrelationSequence *sync;
 
-  if ((tsc < 0) || (tsc > 7))
+  if (tsc > 7)
     return -SIGERR_UNSUPPORTED;
 
   target = 3 + 58 + 16 + 5;
@@ -1945,15 +1943,22 @@ int detectEdgeBurst(signalVector &rxBurst, unsigned tsc, float thresh,
 
 signalVector *downsampleBurst(signalVector &burst)
 {
+  int rc;
   signalVector *in, *out;
 
   in = new signalVector(DOWNSAMPLE_IN_LEN, dnsampler->len());
   out = new signalVector(DOWNSAMPLE_OUT_LEN);
   memcpy(in->begin(), burst.begin(), DOWNSAMPLE_IN_LEN * 2 * sizeof(float));
 
-  dnsampler->rotate((float *) in->begin(), DOWNSAMPLE_IN_LEN,
-                    (float *) out->begin(), DOWNSAMPLE_OUT_LEN);
+  rc = dnsampler->rotate((float *) in->begin(), DOWNSAMPLE_IN_LEN,
+                         (float *) out->begin(), DOWNSAMPLE_OUT_LEN);
   delete in;
+
+  if (rc < 0) {
+    delete out;
+    return NULL;
+  }
+
   return out;
 };