Just comments.

src/dwgpsd.c

@@ -63,6 +63,7 @@
 // release	lib version	API	Raspberry Pi OS
 // 3.22		28		11	bullseye
 // 3.23		29		12
+// 3.24				14			Not tested yet.
 
 #if GPSD_API_MAJOR_VERSION < 5 || GPSD_API_MAJOR_VERSION > 12
 #error libgps API version might be incompatible.

src/encode_aprs.c

@@ -551,6 +551,15 @@ int encode_position (int messaging, int compressed, double lat, double lon, int
 	int result_len = 0;
 
 	if (compressed) {
+
+// Thought:
+// https://groups.io/g/direwolf/topic/92718535#6886
+// When speed is zero, we could put the altitude in the compressed
+// position rather than having /A=999999.
+// However, the resolution would be decreased and that could be important
+// when hiking in hilly terrain.  It would also be confusing to
+// flip back and forth between two different representations.
+
 	  aprs_compressed_pos_t *p = (aprs_compressed_pos_t *)presult;
 
 	  p->dti = messaging ? '=' : '!';

src/fx25_init.c

@@ -371,6 +371,7 @@ int fx25_pick_mode (int fx_mode, int dlen)
 // The PRUG FX.25 TNC has additional modes that will handle larger frames
 // by using multiple RS blocks.  This is a future possibility but needs
 // to be coordinated with other FX.25 developers so we maintain compatibility.
+// See https://web.tapr.org/meetings/DCC_2020/JE1WAZ/DCC-2020-PRUG-FINAL.pptx
 
 	static const int prefer[6] = { 0x04, 0x03, 0x06, 0x09, 0x05, 0x01 };
 	for (int k = 0; k < 6; k++) {