sys/phydat: add unit for mass concentration (g/m^3)

sys/include/phydat.h

@@ -110,7 +110,9 @@ enum {
     UNIT_PPB,       /**< part per billion */
     /* aggregate values */
     UNIT_TIME,      /**< the three dimensions contain sec, min, and hours */
-    UNIT_DATE       /**< the 3 dimensions contain days, months and years */
+    UNIT_DATE,      /**< the 3 dimensions contain days, months and years */
+    /* mass concentration */
+    UNIT_GPM3       /**< grams per cubic meters */
     /* extend this list as needed */
 };
 

sys/phydat/phydat_str.c

@@ -102,6 +102,7 @@ const char *phydat_unit_to_str(uint8_t unit)
         case UNIT_PERCENT:  return "%";
         case UNIT_CTS:      return "cts";
         case UNIT_COULOMB:  return "C";
+        case UNIT_GPM3:     return "g/m^3";
         default:            return "";
     }
 }