[ncp] add new spinel property SPINEL_PROP_MAC_CCA_FAILURE_RATE (#2500)

This commit adds new spinel property corresponding to the MAC CCA
failure rate, and its get handler in `NcpBase`.

doc/spinel-protocol-src/spinel-prop-mac.md

@@ -202,3 +202,9 @@ Structure Parameters:
 * Packed-Encoding: `b`
 * Required capability: `CAP_MAC_WHITELIST`
 
+### PROP 4873: PROP_MAC_CCA_FAILURE_RATE  {#prop-mac-cca-failure-rate}
+ * Type: Read Only
+ * Packed-Encoding: `S`
+
+This property provides the current CCA (Clear Channel Assessment) failure rate.
+Maximum value `0xffff` corresponding to 100% failure rate.

src/ncp/ncp_base.cpp

@@ -92,6 +92,7 @@ const NcpBase::PropertyHandlerEntry NcpBase::mGetPropertyHandlerTable[] =
     NCP_GET_PROP_HANDLER_ENTRY(MAC_SCAN_STATE),
     NCP_GET_PROP_HANDLER_ENTRY(MAC_SCAN_MASK),
     NCP_GET_PROP_HANDLER_ENTRY(MAC_SCAN_PERIOD),
+    NCP_GET_PROP_HANDLER_ENTRY(MAC_CCA_FAILURE_RATE),
 #if OPENTHREAD_ENABLE_MAC_FILTER
     NCP_GET_PROP_HANDLER_ENTRY(MAC_BLACKLIST),
     NCP_GET_PROP_HANDLER_ENTRY(MAC_BLACKLIST_ENABLED),

src/ncp/ncp_base.hpp

@@ -428,6 +428,7 @@ protected:
     NCP_SET_PROP_HANDLER(MAC_SCAN_PERIOD);
     NCP_GET_PROP_HANDLER(MAC_SCAN_STATE);
     NCP_SET_PROP_HANDLER(MAC_SCAN_STATE);
+    NCP_GET_PROP_HANDLER(MAC_CCA_FAILURE_RATE);
 #if OPENTHREAD_ENABLE_MAC_FILTER
     NCP_GET_PROP_HANDLER(MAC_WHITELIST_ENABLED);
     NCP_SET_PROP_HANDLER(MAC_WHITELIST_ENABLED);

src/ncp/ncp_base_mtd.cpp

@@ -1518,6 +1518,11 @@ exit:
 
 #endif // OPENTHREAD_ENABLE_CHANNEL_MONITOR
 
+otError NcpBase::GetPropertyHandler_MAC_CCA_FAILURE_RATE(void)
+{
+    return mEncoder.WriteUint16(otLinkGetCcaFailureRate(mInstance));
+}
+
 otError NcpBase::GetPropertyHandler_CNTR_TX_PKT_TOTAL(void)
 {
     return mEncoder.WriteUint32(otLinkGetCounters(mInstance)->mTxTotal);

src/ncp/spinel.c

@@ -1289,6 +1289,10 @@ spinel_prop_key_to_cstr(spinel_prop_key_t prop_key)
         ret = "PROP_MAC_FIXED_RSS";
         break;
 
+    case SPINEL_PROP_MAC_CCA_FAILURE_RATE:
+        ret = "PROP_MAC_CCA_FAILURE_RATE";
+        break;
+
     case SPINEL_PROP_NET_SAVED:
         ret = "PROP_NET_SAVED";
         break;

src/ncp/spinel.h

@@ -845,7 +845,17 @@ typedef enum
      * * `E`: Optional EUI64 address of node. Set default RSS if not included.
      * * `c`: Fixed RSS. OT_MAC_FILTER_FIXED_RSS_OVERRIDE_DISABLED(127) means not set.
      */
-    SPINEL_PROP_MAC_FIXED_RSS            = SPINEL_PROP_MAC_EXT__BEGIN + 8,
+    SPINEL_PROP_MAC_FIXED_RSS           = SPINEL_PROP_MAC_EXT__BEGIN + 8,
+
+    /// The CCA failure rate
+    /** Format: `S`
+     *
+     * This property provides the current CCA (Clear Channel Assessment) failure rate.
+     *
+     * Maximum value `0xffff` corresponding to 100% failure rate.
+     *
+     */
+    SPINEL_PROP_MAC_CCA_FAILURE_RATE    = SPINEL_PROP_MAC_EXT__BEGIN + 9,
 
     SPINEL_PROP_MAC_EXT__END            = 0x1400,