Add support for radio energy scan API (#749)

* Add support for radio energy scan API

examples/platforms/cc2538/radio.c

@@ -737,3 +737,11 @@ void otPlatRadioClearSrcMatchExtEntries(otInstance *aInstance)
         HWREG(addrAutoPendEn++) = 0;
     }
 }
+
+ThreadError otPlatRadioEnergyScan(otInstance *aInstance, uint8_t aScanChannel, uint16_t aScanDuration)
+{
+    (void)aInstance;
+    (void)aScanChannel;
+    (void)aScanDuration;
+    return kThreadError_NotImplemented;
+}

examples/platforms/posix/radio.c

@@ -763,3 +763,11 @@ void otPlatRadioClearSrcMatchExtEntries(otInstance *aInstance)
 {
     (void)aInstance;
 }
+
+ThreadError otPlatRadioEnergyScan(otInstance *aInstance, uint8_t aScanChannel, uint16_t aScanDuration)
+{
+    (void)aInstance;
+    (void)aScanChannel;
+    (void)aScanDuration;
+    return kThreadError_NotImplemented;
+}

include/platform/radio.h

@@ -89,6 +89,7 @@ typedef enum otRadioCaps
 {
     kRadioCapsNone          = 0,  ///< None
     kRadioCapsAckTimeout    = 1,  ///< Radio supports AckTime event
+    kRadioCapsEnergyScan    = 2,  ///< Radio supports Enegery Scans
 } otRadioCaps;
 
 /**
@@ -436,6 +437,27 @@ extern void otPlatDiagRadioTransmitDone(otInstance *aInstance, bool aFramePendin
  */
 extern void otPlatDiagRadioReceiveDone(otInstance *aInstance, RadioPacket *aPacket, ThreadError aError);
 
+/**
+ * This method begins the energy scan sequence on the radio.
+ *
+ * @param[in] aInstance      The OpenThread instance structure.
+ * @param[in] aScanChannel   The channel to perform the energy scan on.
+ * @param[in] aScanDuration  The duration, in milliseconds, for the channel to be scanned.
+ *
+ * @retval ::kThreadError_None            Successfully started scanning the channel.
+ * @retval ::kThreadError_NotImplemented  The radio doesn't support energy scanning.
+ */
+ThreadError otPlatRadioEnergyScan(otInstance *aInstance, uint8_t aScanChannel, uint16_t aScanDuration);
+
+/**
+ * The radio driver calls this method to notify OpenThread that the energy scan is complete.
+ *
+ * @param[in]  aInstance           The OpenThread instance structure.
+ * @param[in]  aEnergyScanMaxRssi  The maximum RSSI encountered on the scanned channel.
+ *
+ */
+extern void otPlatRadioEnergyScanDone(otInstance *aInstance, int8_t aEnergyScanMaxRssi);
+
 /**
  * @}
  *

src/core/mac/mac.cpp

@@ -222,10 +222,66 @@ bool Mac::IsEnergyScanInProgress(void)
 void Mac::StartEnergyScan(void)
 {
     mState = kStateEnergyScan;
-    mEnergyScanCurrentMaxRssi = kInvalidRssiValue;
-    mMacTimer.Start(mScanDuration);
-    mEnergyScanSampleRssiTask.Post();
-    NextOperation();
+
+    if (!(otPlatRadioGetCaps(mNetif.GetInstance()) & kRadioCapsEnergyScan))
+    {
+        mEnergyScanCurrentMaxRssi = kInvalidRssiValue;
+        mMacTimer.Start(mScanDuration);
+        mEnergyScanSampleRssiTask.Post();
+        NextOperation();
+    }
+    else
+    {
+        ThreadError error = otPlatRadioEnergyScan(mNetif.GetInstance(), mScanChannel, mScanDuration);
+
+        if (error != kThreadError_None)
+        {
+            // Cancel scan
+            mEnergyScanHandler(mScanContext, NULL);
+            ScheduleNextTransmission();
+        }
+    }
+}
+
+extern "C" void otPlatRadioEnergyScanDone(otInstance *aInstance, int8_t aEnergyScanMaxRssi)
+{
+    aInstance->mThreadNetif.GetMac().EnergyScanDone(aEnergyScanMaxRssi);
+}
+
+void Mac::EnergyScanDone(int8_t aEnergyScanMaxRssi)
+{
+    // Trigger a energy scan handler callback if necessary
+    if (aEnergyScanMaxRssi != kInvalidRssiValue)
+    {
+        otEnergyScanResult result;
+
+        result.mChannel = mScanChannel;
+        result.mMaxRssi = aEnergyScanMaxRssi;
+        mEnergyScanHandler(mScanContext, &result);
+    }
+
+    // Update to the next scan channel
+    do
+    {
+        mScanChannels >>= 1;
+        mScanChannel++;
+
+        // If we have scanned all the channels, then fire the final callback
+        // and start the next transmission task
+        if (mScanChannels == 0 || mScanChannel > kPhyMaxChannel)
+        {
+            mEnergyScanHandler(mScanContext, NULL);
+            ScheduleNextTransmission();
+            ExitNow();
+        }
+    }
+    while ((mScanChannels & 1) == 0);
+
+    // Start scanning the next channel
+    StartEnergyScan();
+
+exit:
+    return;
 }
 
 void Mac::HandleEnergyScanSampleRssi(void *aContext)
@@ -769,31 +825,7 @@ void Mac::HandleMacTimer(void)
         break;
 
     case kStateEnergyScan:
-        if (mEnergyScanCurrentMaxRssi != kInvalidRssiValue)
-        {
-            otEnergyScanResult result;
-
-            result.mChannel = mScanChannel;
-            result.mMaxRssi = mEnergyScanCurrentMaxRssi;
-            mEnergyScanHandler(mScanContext, &result);
-        }
-
-        do
-        {
-            mScanChannels >>= 1;
-            mScanChannel++;
-
-            if (mScanChannels == 0 || mScanChannel > kPhyMaxChannel)
-            {
-                mEnergyScanHandler(mScanContext, NULL);
-                ScheduleNextTransmission();
-                ExitNow();
-            }
-        }
-        while ((mScanChannels & 1) == 0);
-
-        mEnergyScanCurrentMaxRssi = kInvalidRssiValue;
-        mMacTimer.Start(mScanDuration);
+        EnergyScanDone(mEnergyScanCurrentMaxRssi);
         break;
 
     case kStateTransmitData:

src/core/mac/mac.hpp

@@ -235,6 +235,14 @@ public:
      */
     ThreadError EnergyScan(uint32_t aScanChannels, uint16_t aScanDuration, EnergyScanHandler aHandler, void *aContext);
 
+    /**
+     * This function indicates the energy scan for the current channel is complete.
+     *
+     * @param[in]  aEnergyScanMaxRssi  The maximum RSSI encountered on the scanned channel.
+     *
+     */
+    void EnergyScanDone(int8_t aEnergyScanMaxRssi);
+
     /**
      * This method indicates whether or not rx-on-when-idle is enabled.
      *

tests/unit/test_platform.cpp

@@ -204,6 +204,11 @@ extern "C" {
         (void)aInstance;
     }
 
+    ThreadError otPlatRadioEnergyScan(otInstance *, uint8_t, uint16_t)
+    {
+        return kThreadError_NotImplemented;
+    }
+
     //
     // Random
     //