#define  V2_CLOCK_RATE_SHIFT                   3
 #define  V2_CLOCK_SRC_MASK                     0x00000007
 #define  V2_CLOCK_SRC_SHIFT                    0
+#define   V2_CLOCK_SRC_AESEBU_ON_XLR           0x07
+#define   V2_CLOCK_SRC_ADAT_ON_DSUB            0x05
+#define   V2_CLOCK_SRC_WORD_ON_BNC             0x04
+#define   V2_CLOCK_SRC_SPH                     0x03
+#define   V2_CLOCK_SRC_SPDIF                   0x02    // on either coaxial or optical
+#define   V2_CLOCK_SRC_ADAT_ON_OPT             0x01
+#define   V2_CLOCK_SRC_INTERNAL                        0x00
 #define  V2_CLOCK_FETCH_ENABLE                 0x02000000
 #define  V2_CLOCK_MODEL_SPECIFIC               0x04000000
 
                            enum snd_motu_clock_source *src)
 {
        switch (data & V2_CLOCK_SRC_MASK) {
-       case 0:
+       case V2_CLOCK_SRC_INTERNAL:
                *src = SND_MOTU_CLOCK_SOURCE_INTERNAL;
                break;
-       case 1:
+       case V2_CLOCK_SRC_ADAT_ON_OPT:
                *src = SND_MOTU_CLOCK_SOURCE_ADAT_ON_OPT;
                break;
-       case 2:
+       case V2_CLOCK_SRC_SPDIF:
        {
                bool support_iec60958_on_opt = (motu->spec == &snd_motu_spec_828mk2 ||
                                                motu->spec == &snd_motu_spec_traveler);
                }
                break;
        }
-       case 3:
+       case V2_CLOCK_SRC_SPH:
                *src = SND_MOTU_CLOCK_SOURCE_SPH;
                break;
-       case 4:
+       case V2_CLOCK_SRC_WORD_ON_BNC:
                *src = SND_MOTU_CLOCK_SOURCE_WORD_ON_BNC;
                break;
-       case 5:
+       case V2_CLOCK_SRC_ADAT_ON_DSUB:
                *src = SND_MOTU_CLOCK_SOURCE_ADAT_ON_DSUB;
                break;
-       case 7:
+       case V2_CLOCK_SRC_AESEBU_ON_XLR:
                *src = SND_MOTU_CLOCK_SOURCE_AESEBU_ON_XLR;
                break;
        default: