Export redesign

this is an atempt to make the export of functions typesafe.
I replaced the jumptable void ** by a struct (jt_funcs) with function pointers.
The EXPORT_FUNC macro now has 3 fixed parameters and one
variadic parameter
The first is the name of the exported function,
the rest of the parameters are used to format a functionpointer
in the jumptable,

the EXPORT_FUNC macros are expanded three times,
1. to declare the members of the struct
2. to initialize the structmember pointers
3. to call the functions in stubs.c

Signed-off-by: Martin Dorwig <dorwig@tetronik.com>
Acked-by: Simon Glass <sjg@chromium.org>

Signed-off-by: Simon Glass <sjg@chromium.org>
(resending to the list since my tweaks are not quite trivial)
diff --git a/include/exports.h b/include/exports.h
index 41d5085..205affe 100644
--- a/include/exports.h
+++ b/include/exports.h
@@ -3,6 +3,8 @@
 
 #ifndef __ASSEMBLY__
 
+struct spi_slave;
+
 /* These are declarations of exported functions available in C code */
 unsigned long get_version(void);
 int  getc(void);
@@ -10,22 +12,23 @@
 void putc(const char);
 void puts(const char*);
 int printf(const char* fmt, ...);
-void install_hdlr(int, void (*interrupt_handler_t)(void *), void*);
+void install_hdlr(int, interrupt_handler_t, void*);
 void free_hdlr(int);
 void *malloc(size_t);
 void free(void*);
 void __udelay(unsigned long);
 unsigned long get_timer(unsigned long);
 int vprintf(const char *, va_list);
-unsigned long simple_strtoul(const char *cp,char **endp,unsigned int base);
+unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base);
 int strict_strtoul(const char *cp, unsigned int base, unsigned long *res);
 char *getenv (const char *name);
 int setenv (const char *varname, const char *varvalue);
-long simple_strtol(const char *cp,char **endp,unsigned int base);
-int strcmp(const char * cs,const char * ct);
+long simple_strtol(const char *cp, char **endp, unsigned int base);
+int strcmp(const char *cs, const char *ct);
 unsigned long ustrtoul(const char *cp, char **endp, unsigned int base);
 unsigned long long ustrtoull(const char *cp, char **endp, unsigned int base);
-#if defined(CONFIG_CMD_I2C)
+#if defined(CONFIG_CMD_I2C) && \
+		(!defined(CONFIG_DM_I2C) || defined(CONFIG_DM_I2C_COMPAT))
 int i2c_write (uchar, uint, int , uchar* , int);
 int i2c_read (uchar, uint, int , uchar* , int);
 #endif
@@ -34,15 +37,14 @@
 
 #endif    /* ifndef __ASSEMBLY__ */
 
-enum {
-#define EXPORT_FUNC(x) XF_ ## x ,
+struct jt_funcs {
+#define EXPORT_FUNC(impl, res, func, ...) res(*func)(__VA_ARGS__);
 #include <_exports.h>
 #undef EXPORT_FUNC
-
-	XF_MAX
 };
 
-#define XF_VERSION	6
+
+#define XF_VERSION	7
 
 #if defined(CONFIG_X86)
 extern gd_t *global_data;