From f69edaae7bbb22601e8b213a342ebd3ba4df780a Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Tue, 26 Aug 2014 14:15:52 -0400
Subject: Eliminate reverse linkage of gpsd_write. All regression tests pass.

---
 gpsctl.c       | 8 --------
 gpsd.c         | 8 --------
 gpsd.h-tail    | 2 ++
 gpsdecode.c    | 8 --------
 gpsmon.c       | 3 ++-
 libgpsd_core.c | 9 +++++++++
 test_geoid.c   | 8 --------
 test_packet.c  | 8 --------
 8 files changed, 13 insertions(+), 41 deletions(-)

diff --git a/gpsctl.c b/gpsctl.c
index 910d5004..4cd7fb33 100644
--- a/gpsctl.c
+++ b/gpsctl.c
@@ -30,14 +30,6 @@ static unsigned int timeout = 0;	/* no timeout */
 static struct gps_context_t context;
 static bool hunting = true;
 
-ssize_t gpsd_write(struct gps_device_t *session,
-		   const char *buf,
-		   const size_t len)
-/* pass low-level data to devices straight through */
-{
-    return gpsd_serial_write(session, buf, len);
-}
-
 /*
  * Set this as high or higher than the maximum number of subtype
  * probes in drivers.c.
diff --git a/gpsd.c b/gpsd.c
index ced2c608..787bdc82 100644
--- a/gpsd.c
+++ b/gpsd.c
@@ -165,14 +165,6 @@ static void onsig(int sig)
     signalled = (sig_atomic_t) sig;
 }
 
-ssize_t gpsd_write(struct gps_device_t *session,
-		   const char *buf,
-		   const size_t len)
-/* pass low-level data to devices straight through */
-{
-    return gpsd_serial_write(session, buf, len);
-}
-
 void gpsd_report(const int debuglevel, const int errlevel,
 		 const char *fmt, ...)
 {
diff --git a/gpsd.h-tail b/gpsd.h-tail
index 503bbbef..00c9a9b9 100644
--- a/gpsd.h-tail
+++ b/gpsd.h-tail
@@ -268,6 +268,8 @@ struct gps_context_t {
      * and we don't want them reordered either */
     /*@reldef@*/volatile char *shmexport;
 #endif
+    ssize_t (*serial_write)(struct gps_device_t *,
+			    const char *buf, const size_t len);
 };
 
 /* state for resolving interleaved Type 24 packets */
diff --git a/gpsdecode.c b/gpsdecode.c
index b65e1f46..67ac16da 100644
--- a/gpsdecode.c
+++ b/gpsdecode.c
@@ -27,14 +27,6 @@ static unsigned int typelist[32];
  *
  **************************************************************************/
 
-ssize_t gpsd_write(struct gps_device_t *session,
-		   const char *buf,
-		   const size_t len)
-/* pass low-level data to devices straight through */
-{
-    return gpsd_serial_write(session, buf, len);
-}
-
 void gpsd_report(const int debuglevel, const int errlevel,
 		 const char *fmt, ...)
 {
diff --git a/gpsmon.c b/gpsmon.c
index 37d6b1aa..cfcaa8e2 100644
--- a/gpsmon.c
+++ b/gpsmon.c
@@ -639,7 +639,7 @@ void gpsd_report(const int debuglevel, const int errlevel, const char *fmt, ...)
     }
 }
 
-ssize_t gpsd_write(struct gps_device_t *session,
+static ssize_t gpsmon_serial_write(struct gps_device_t *session,
 		   const char *buf,
 		   const size_t len)
 /* pass low-level data to devices, echoing it to the log window */
@@ -1099,6 +1099,7 @@ int main(int argc, char **argv)
     (void)putenv("TZ=UTC");	// for ctime()
     /*@ +observertrans @*/
     gps_context_init(&context);	// initialize the report mutex
+    context.serial_write = gpsmon_serial_write;
     while ((option = getopt(argc, argv, "aD:LVhl:nt:?")) != -1) {
 	switch (option) {
 	case 'a':
diff --git a/libgpsd_core.c b/libgpsd_core.c
index f11e4831..5af50977 100644
--- a/libgpsd_core.c
+++ b/libgpsd_core.c
@@ -35,6 +35,14 @@
 #include "driver_nmea2000.h"
 #endif /* defined(NMEA2000_ENABLE) */
 
+ssize_t gpsd_write(struct gps_device_t *session,
+		   const char *buf,
+		   const size_t len)
+/* pass low-level data to devices straight through */
+{
+    return session->context->serial_write(session, buf, len);
+}
+
 #if defined(PPS_ENABLE)
 static pthread_mutex_t report_mutex;
 
@@ -248,6 +256,7 @@ void gps_context_init(struct gps_context_t *context)
 #ifdef SHM_EXPORT_ENABLE
 	.shmexport      = NULL,
 #endif /* SHM_EXPORT_ENABLE */
+	.serial_write    = gpsd_serial_write,
     };
     /*@ +initallelements +nullassign +nullderef @*/
     /* *INDENT-ON* */
diff --git a/test_geoid.c b/test_geoid.c
index 2392b1a8..19e926ba 100644
--- a/test_geoid.c
+++ b/test_geoid.c
@@ -10,14 +10,6 @@
 
 #include "gpsd.h"
 
-ssize_t gpsd_write(struct gps_device_t *session,
-		   const char *buf,
-		   const size_t len)
-/* pass low-level data to devices straight through */
-{
-    return gpsd_serial_write(session, buf, len);
-}
-
 void gpsd_report(const int debuglevel, const int errlevel,
 		 const char *fmt, ...)
 {
diff --git a/test_packet.c b/test_packet.c
index 2228ddbf..13c3e7bc 100644
--- a/test_packet.c
+++ b/test_packet.c
@@ -17,14 +17,6 @@
 
 static int verbose = 0;
 
-ssize_t gpsd_write(struct gps_device_t *session,
-		   const char *buf,
-		   const size_t len)
-/* pass low-level data to devices straight through */
-{
-    return gpsd_serial_write(session, buf, len);
-}
-
 void gpsd_report(int debuglevel, int errlevel, const char *fmt, ...)
 /* assemble command in printf(3) style, use stderr or syslog */
 {
-- 
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