Tested compatibility with gpsd 3.25.

Author: wb2osz

src/dwgpsd.c

@@ -57,18 +57,35 @@
 
 
 
-// An incompatibility was introduced with version 7
-// and again with 9 and again with 10.
-
-// 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.
+// An API incompatibility was introduced with API version 7.
+// and again with 9.
+// and again with 10.
+// We deal with it by using a bunch of conditional code such as:
+//	#if GPSD_API_MAJOR_VERSION >= 9
+
+
+// release	lib version	API	Raspberry Pi OS		Testing status
+// 3.22		28		11	bullseye		OK.
+// 3.23		29		12				OK.
+// 3.25		30		14				OK, Jan. 2023
+
+// Previously the compilation would fail if the API version was later
+// than the last one tested.  Now it is just a warning because it changes so
+// often but more recent versions have not broken backward compatibility.
+
+#define MAX_TESTED_VERSION 14
+
+#if (GPSD_API_MAJOR_VERSION < 5) || (GPSD_API_MAJOR_VERSION > MAX_TESTED_VERSION)
+#pragma message "Your version of gpsd might be incompatible with this application."
+#pragma message "The libgps application program interface (API) often"
+#pragma message "changes to be incompatible with earlier versions."
+// I could not figure out how to do value substitution here.
+#pragma message "You have libgpsd API version GPSD_API_MAJOR_VERSION."
+#pragma message "The last that has been tested is MAX_TESTED_VERSION."
+#pragma message "Even if this builds successfully, it might not run properly."
 #endif
 
+
 /*
  * Information for interface to gpsd daemon.
  */
@@ -168,6 +185,22 @@ static void * read_gpsd_thread (void *arg);
  *	can't find it there.  Solution  is to define environment variable:
  *
  *	export LD_LIBRARY_PATH=/use/local/lib
+ *
+ * January 2023: Now using 64 bit Raspberry Pi OS, bullseye.
+ * See   https://gitlab.com/gpsd/gpsd/-/blob/master/build.adoc
+ * Try to install in proper library place so we don't have to mess with LD_LIBRARY_PATH.
+ *
+ *      (Remove any existing gpsd first so we are not mixing mismatched pieces.)
+ *
+ * 	sudo apt-get install libncurses5-dev
+ *	sudo apt-get install gtk+-3.0
+ *
+ * 	git clone https://gitlab.com/gpsd/gpsd.git  gpsd-gitlab
+ * 	cd gpsd-gitlab
+ * 	scons prefix=/usr libdir=lib/aarch64-linux-gnu
+ *	[ scons check ]
+ *	sudo scons udev-install
+ *	
  */