diff --git a/src/stlink-hw.h b/src/stlink-hw.h
index 83146f3..dd17d20 100644
--- a/src/stlink-hw.h
+++ b/src/stlink-hw.h
@@ -87,7 +87,28 @@ typedef struct {
 
 typedef uint32_t stm32_addr_t;
 
-struct stlink {
+enum transport_type
+{
+  TRANSPORT_TYPE_ZERO = 0,
+#if CONFIG_USE_LIBSG
+  TRANSPORT_TYPE_LIBSG,
+#endif /* CONFIG_USE_LIBSG */
+#if CONFIG_USE_LIBUSB
+  TRANSPORT_TYPE_LIBUSB,
+#endif /* CONFIG_USE_LIBUSB */
+  TRANSPORT_TYPE_INVALID
+};
+
+struct stlink_libusb
+{
+  libusb_device_handle* usb_handle;
+  struct libusb_transfer* req_trans;
+  struct libusb_transfer* rep_trans;
+  unsigned int ep_req;
+  unsigned int ep_rep;
+};
+
+struct stlink_libsg {
 	int sg_fd;
 	int do_scsi_pt_err;
 	// sg layer verboseness: 0 for no debug info, 10 for lots
@@ -136,7 +157,27 @@ struct stlink {
 	size_t sram_size;
 };
 
-struct stlink* stlink_quirk_open(const char *dev_name, const int verbose);
+struct stlink
+{
+        enum transport_type tt;
+        union {
+#if CONFIG_USE_LIBUSB
+            struct stlink_libusb *libusb;
+#endif /* CONFIG_USE_LIBUSB */
+#if CONFIG_USE_LIBSG
+            struct stlink_libsg *libsg;
+#endif /* CONFIG_USE_LIBSG */
+        } transport;
+
+        unsigned char q_buf[64];
+        size_t q_len;
+
+        /* layer independant */
+        uint32_t core_id;
+};
+
+
+struct stlink* stlink_quirk_open(enum transport_type tt, const char *dev_name, const int verbose);
 int stlink_current_mode(struct stlink *sl);
 void stlink_enter_swd_mode(struct stlink *sl);
 void stlink_enter_jtag_mode(struct stlink *sl);
diff --git a/stm32l/build/Makefile b/stm32l/build/Makefile
index e731ce6..c50d61a 100644
--- a/stm32l/build/Makefile
+++ b/stm32l/build/Makefile
@@ -1,6 +1,7 @@
 PRG := stm32l
 DEBUG := # -DDEBUG
 CONFIG := -DCONFIG_USE_LIBUSB=1
+CFLAGS+= -I../../src
 
 all: $(PRG)
 
@@ -16,7 +17,7 @@ $(PRG): $(OBJS)
 %.o: ../src/%.c
 	gcc -O3 -g3 -Wall -Werror -c -std=gnu99 -MMD -MP \
 		-fno-strict-aliasing -Wno-unused $(DEBUG) $(CONFIG) \
-		-I$(HOME)/install/include \
+                $(CFLAGS) \
 		-MF"$(@:%.o=%.d)" -MT"$(@:%.o=%.d)"\
 		-o "$@" "$<"
 
diff --git a/stm32l/src/main.c b/stm32l/src/main.c
index 127841b..9a68aa0 100644
--- a/stm32l/src/main.c
+++ b/stm32l/src/main.c
@@ -78,15 +78,6 @@ static uint16_t read_uint16(const unsigned char *c, const int pt)
 
 libusb_context* libusb_ctx =  NULL;
 
-struct stlink_libusb
-{
-  libusb_device_handle* usb_handle;
-  struct libusb_transfer* req_trans;
-  struct libusb_transfer* rep_trans;
-  unsigned int ep_req;
-  unsigned int ep_rep;
-};
-
 struct trans_ctx
 {
 #define TRANS_FLAGS_IS_DONE (1 << 0)
@@ -209,40 +200,7 @@ static inline int send_only
 }
 
 
-/* stlink layer independant interface */
-
-enum transport_type
-{
-  TRANSPORT_TYPE_ZERO = 0,
-#if CONFIG_USE_LIBSG
-  TRANSPORT_TYPE_LIBSG,
-#endif /* CONFIG_USE_LIBSG */
-#if CONFIG_USE_LIBUSB
-  TRANSPORT_TYPE_LIBUSB,
-#endif /* CONFIG_USE_LIBUSB */
-  TRANSPORT_TYPE_INVALID
-};
-
-struct stlink
-{
-  enum transport_type tt;
-  union
-  {
-#if CONFIG_USE_LIBUSB
-    struct stlink_libusb libusb;
-#endif /* CONFIG_USE_LIBUSB */
-#if CONFIG_USE_LIBSG
-    void* libsg;
-#endif /* CONFIG_USE_LIBSG */
-  } transport;
-
-  unsigned char q_buf[64];
-  size_t q_len;
-
-  /* layer independant */
-  uint32_t core_id;
-};
-
+// KARL - fixme, common code! (or, one per backend)
 int stlink_initialize(enum transport_type tt)
 {
   switch (tt)
@@ -266,6 +224,7 @@ int stlink_initialize(enum transport_type tt)
   return 0;
 }
 
+// candidate for common code...
 void stlink_finalize(enum transport_type tt)
 {
   switch (tt)
@@ -302,15 +261,15 @@ static int is_stlink_device(libusb_device* dev)
 }
 #endif /* CONFIG_USE_LIBUSB */
 
-/* fwd decl */
-void stlink_close(struct stlink*);
 
 struct stlink* stlink_quirk_open
 (enum transport_type tt, const char *dev_name, const int verbose)
 {
   struct stlink* sl = NULL;
+  struct stlink_libusb* slu = NULL;
 
   sl = malloc(sizeof(struct stlink));
+  slu = malloc(sizeof(struct stlink_libusb));
   if (sl == NULL) goto on_error;
 
   sl->tt = tt;
@@ -320,7 +279,6 @@ struct stlink* stlink_quirk_open
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
 
       int error = -1;
 
@@ -344,7 +302,7 @@ struct stlink* stlink_quirk_open
       }
       if (i == count) return NULL;
 
-      if (libusb_open(dev, &slu->usb_handle))
+      if (libusb_open(dev, &(slu->usb_handle)))
       {
 	printf("libusb_open()\n");
 	goto on_libusb_error;
@@ -404,6 +362,7 @@ struct stlink* stlink_quirk_open
 	stlink_close(sl);
 	return NULL;
       }
+      sl->transport.libusb = slu;
 
       break ;
     }
@@ -434,7 +393,7 @@ void stlink_close(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const handle = &sl->transport.libusb;
+      struct stlink_libusb* const handle = sl->transport.libusb;
 
       if (handle->req_trans != NULL)
 	libusb_free_transfer(handle->req_trans);
@@ -469,7 +428,7 @@ void stlink_version(struct stlink* sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -509,7 +468,7 @@ int stlink_current_mode(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf; 
       ssize_t size;
 
@@ -548,7 +507,7 @@ void stlink_core_id(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf; 
       ssize_t size;
 
@@ -584,7 +543,7 @@ void stlink_status(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -621,7 +580,7 @@ void stlink_enter_swd_mode(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -653,7 +612,7 @@ void stlink_exit_dfu_mode(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -683,7 +642,7 @@ void stlink_reset(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -713,7 +672,7 @@ void stlink_step(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -743,7 +702,7 @@ void stlink_run(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -773,7 +732,7 @@ void stlink_exit_debug_mode(struct stlink *sl)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;
 
@@ -815,7 +774,7 @@ void stlink_read_mem32(struct stlink *sl, uint32_t addr, uint16_t len)
 #if CONFIG_USE_LIBUSB
   case TRANSPORT_TYPE_LIBUSB:
     {
-      struct stlink_libusb* const slu = &sl->transport.libusb;
+      struct stlink_libusb* const slu = sl->transport.libusb;
       unsigned char* const buf = sl->q_buf;
       ssize_t size;