Add support for GDB monitor-style I/O.

* m68k/idp-outbyte.c (raw_outbyte): Renamed from outbyte; made
static.
(outbyte): Call raw_outbyte; if GDB_MONITOR_OUTPUT is #defined,
precede the byte with a ^O character.
* m68k/idpgdb.ld: New linker script.
* m68k/Makefile.in (IDPGDB_LDFLAGS, IDPGDB_BSP, IDPGDB_OBJS): New
variables.
(all): Add ${IDPGDB_BSP} to the list of things to build.
(${IDPGDB_BSP}, idp-gdb-outbyte.o, idpgdb-test.x,
idpgdb-test.srec, idpgdb-test.dis, idpgdb-test): New rules.
(install): Install the IDPGDB stuff, too.

libgloss/m68k/idp-outbyte.c

@@ -28,15 +28,47 @@
 #define WRITEREG(x, y)	(*((char *) DUART_ADDR + (x * 4) + 3) = y)
 
 /*
- * outbyte -- send a byte to the DUART buffer. This only sends
+ * raw_outbyte -- send a byte to the DUART buffer. This only sends
  *           to channel A.
  */
-void
-_DEFUN (outbyte, (byte),
+static void
+_DEFUN (raw_outbyte, (byte),
 	char byte)
 {
+  /* First, wait for the UART to finish clocking out the last
+     character we sent, if any.  Then, give it the next character to
+     work on.  By waiting first, then handing off a new character, we
+     allow the UART to work while the processor (perhaps) does other
+     things; if we waited after sending each character, there'd be no
+     opportunity for parallelism.  */
   while ((READREG (DUART_SRA) & 0x04) == 0x00)
     ;
 
   WRITEREG (DUART_TBA, byte);		/* write the byte */
 }
+
+
+/*
+ * outbyte -- send BYTE out the DUART's channel A, for display to
+ *      the user.
+ *
+ *      Normally, this is identical to raw_outbyte, but if
+ *      GDB_MONITOR_OUTPUT is #defined, we prefix each byte we send
+ *      with a ^O character (ASCII 15).  This is a signal to GDB's
+ *      `rom68k' target to pass the character directly on to the user;
+ *      it allows programs to do console output under GDB.
+ *
+ *      We compile this file twice: once with GDB_MONITOR_OUTPUT
+ *      #defined, and once without.  The former .o file we put in
+ *      libidpgdb.a, which is included in the link by idpgdb.ld; the
+ *      latter we put in libidp.a, which is selected by idp.ld.
+ */
+void
+_DEFUN (outbyte, (byte),
+        char byte)
+{
+#ifdef GDB_MONITOR_OUTPUT
+  raw_outbyte (0x0f);
+#endif
+  raw_outbyte (byte);
+}