https://sourceforge.net/p/vice-emu/code/45435/

--- vice/src/Makefile.am
+++ vice/src/Makefile.am
@@ -594,6 +594,7 @@
 resid_lib = $(top_builddir)/src/resid/libresid.a
 resid_dtv_lib = $(top_builddir)/src/resid-dtv/libresiddtv.a
 rs232drv_lib = $(top_builddir)/src/rs232drv/librs232drv.a
+rs232drvpet_lib = $(top_builddir)/src/rs232drv/librs232drvpet.a
 raster_lib = $(top_builddir)/src/raster/libraster.a
 rtc_lib = $(top_builddir)/src/core/rtc/librtc.a
 samplerdrv_lib = $(top_builddir)/src/samplerdrv/libsamplerdrv.a
@@ -631,7 +632,7 @@
 # external libraries required for all emulators
 emu_extlibs = @UI_LIBS@ @SDL_EXTRA_LIBS@ @SOUND_LIBS@ @JOY_LIBS@ @GFXOUTPUT_LIBS@ @ZLIB_LIBS@ @DYNLIB_LIBS@ @ARCH_LIBS@ $(archdep_lib) $(linenoise_ng_lib)
 
-driver_libs = $(joyport_lib) $(samplerdrv_lib) $(sounddrv_lib) $(mididrv_lib) $(socketdrv_lib) $(hwsiddrv_lib) $(gfxoutputdrv_lib) $(printerdrv_lib) $(rs232drv_lib) $(diskimage_lib) $(fsdevice_lib) $(tape_lib) $(fileio_lib) $(serial_lib) $(core_lib)
+driver_libs = $(joyport_lib) $(samplerdrv_lib) $(sounddrv_lib) $(mididrv_lib) $(socketdrv_lib) $(hwsiddrv_lib) $(gfxoutputdrv_lib) $(printerdrv_lib) $(diskimage_lib) $(fsdevice_lib) $(tape_lib) $(fileio_lib) $(serial_lib) $(core_lib)
 
 if SUPPORT_X64
 x64_bin = x64
@@ -716,6 +717,7 @@
 	$(sid_lib) \
 	$(monitor_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(vicii_lib) \
 	$(raster_lib) \
 	$(userport_lib) \
@@ -773,6 +775,7 @@
 	$(sid_lib) \
 	$(monitor_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(viciisc_lib) \
 	$(raster_lib) \
 	$(userport_lib) \
@@ -895,6 +898,7 @@
 	$(sid_lib) \
 	$(monitor_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(viciisc_lib) \
 	$(raster_lib) \
 	$(userport_lib) \
@@ -954,6 +958,7 @@
 	$(sid_lib) \
 	$(monitor_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(vicii_lib) \
 	$(vdc_lib) \
 	$(raster_lib) \
@@ -1011,6 +1016,7 @@
 	$(monitor_lib) \
 	$(sid_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(raster_lib) \
 	$(userport_lib) \
 	$(diag_lib) \
@@ -1063,6 +1069,7 @@
 	$(monitor_lib) \
 	$(sid_lib) \
 	$(driver_libs) \
+	$(rs232drvpet_lib) \
 	$(crtc_lib) \
 	$(raster_lib) \
 	$(video_lib) \
@@ -1122,6 +1129,7 @@
 	$(monitor_lib) \
 	$(sid_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(raster_lib) \
 	$(rtc_lib) \
 	$(video_lib) \
@@ -1180,6 +1188,7 @@
 	$(monitor_lib) \
 	$(sid_lib) \
 	$(driver_libs) \
+	$(rs232drvpet_lib) \
 	$(crtc_lib) \
 	$(raster_lib) \
 	$(video_lib) \
@@ -1236,6 +1245,7 @@
 	$(xcbm5x0_lib) \
 	$(sid_lib) \
 	$(driver_libs) \
+	$(rs232drv_lib) \
 	$(vicii_lib) \
 	$(raster_lib) \
 	$(rtc_lib) \
@@ -1540,8 +1550,11 @@
 	@echo "making all in printerdrv"
 	@(cd printerdrv && $(MAKE))
 $(rs232drv_lib):
-	@echo "making all in rs232drv"
-	@(cd rs232drv && $(MAKE))
+	@echo "making librs232drv.a in rs232drv"
+	@(cd rs232drv && $(MAKE) librs232drv.a)
+$(rs232drvpet_lib):
+	@echo "making librs232drvpet.a in rs232drv"
+	@(cd rs232drv && $(MAKE) librs232drvpet.a)
 $(raster_lib):
 	@echo "making libraster.a in raster"
 	@(cd raster && $(MAKE) libraster.a)
--- vice/src/c64/Makefile.am
+++ vice/src/c64/Makefile.am
@@ -216,8 +216,6 @@
 	c64fastiec.h \
 	c64keyboard.c \
 	c64keyboard.h \
-	c64parallel.c \
-	c64parallel.h \
 	c64rom.c \
 	c64rom.h \
 	c64romset.c \
--- vice/src/c64dtv/c64dtv.c
+++ vice/src/c64dtv/c64dtv.c
@@ -89,7 +89,6 @@
 #include "protopad.h"
 #include "ps2mouse.h"
 #include "resources.h"
-#include "rs232drv.h"
 #include "rushware_keypad.h"
 #include "sampler.h"
 #include "sampler2bit.h"
@@ -422,10 +421,12 @@
         init_resource_fail("sid");
         return -1;
     }
+#if 0
     if (rs232drv_resources_init() < 0) {
         init_resource_fail("rs232drv");
         return -1;
     }
+#endif
     if (serial_resources_init() < 0) {
         init_resource_fail("serial");
         return -1;
@@ -528,7 +529,9 @@
     flash_trap_resources_shutdown();
     c64dtv_resources_shutdown();
     c64dtvmem_resources_shutdown();
+#if 0
     rs232drv_resources_shutdown();
+#endif
     printer_resources_shutdown();
     drive_resources_shutdown();
     fsdevice_resources_shutdown();
@@ -562,10 +565,12 @@
         init_cmdline_options_fail("sid");
         return -1;
     }
+#if 0
     if (rs232drv_cmdline_options_init() < 0) {
         init_cmdline_options_fail("rs232drv");
         return -1;
     }
+#endif
     if (serial_cmdline_options_init() < 0) {
         init_cmdline_options_fail("serial");
         return -1;
@@ -712,8 +717,10 @@
         return -1;
     }
 
+#if 0
     /* Initialize RS232 handler.  */
     rs232drv_init();
+#endif
 
     /* Initialize print devices.  */
     printer_init();
@@ -798,8 +805,9 @@
     ciacore_reset(machine_context.cia2);
     sid_reset();
 
+#if 0
     rs232drv_reset();
-
+#endif
     printer_reset();
 
     /* FIXME */
--- vice/src/rs232drv/Makefile.am
+++ vice/src/rs232drv/Makefile.am
@@ -14,7 +14,7 @@
 AM_LDFLAGS = @VICE_LDFLAGS@
 
 
-noinst_LIBRARIES = librs232drv.a
+noinst_LIBRARIES = librs232drv.a librs232drvpet.a
 
 librs232drv_a_SOURCES = \
 	rs232dev.h \
@@ -26,3 +26,16 @@
 	rs232net.h \
 	rsuser.c \
 	rsuser.h
+
+# Same as above, but without the userport bits, to avoid registering userport
+# resources and command line options with xpet and xcbm2 (these have stubs for
+# rsuser_resources_init() and rsuser_cmdline_init()
+librs232drvpet_a_SOURCES = \
+	rs232dev.h \
+	rs232.c \
+	rs232.h \
+	rs232drv.c \
+	rs232drv.h \
+	rs232net.c \
+	rs232net.h \
+	rsuser.h