SetCommConfig has 3 arguments, not 2.

dlls/kernel/comm.c

@@ -1824,8 +1824,9 @@ BOOL WINAPI GetCommConfig(
  *  True on success, false if the handle was bad is not a communications device.
  */
 BOOL WINAPI SetCommConfig(
-    HANDLE       hFile,        /* [in] The communications device. */
-    LPCOMMCONFIG lpCommConfig) /* [in] The desired configuration. */
+    HANDLE       hFile,		/* [in] The communications device. */
+    LPCOMMCONFIG lpCommConfig,	/* [in] The desired configuration. */
+    DWORD dwSize) 		/* [in] size of the lpCommConfig struct */
 {
     TRACE("(%x %p)\n",hFile,lpCommConfig);
     return SetCommState(hFile,&lpCommConfig->dcb);

dlls/kernel/kernel32.spec

@@ -660,7 +660,7 @@ debug_channels (comm debugstr dll int resource stress thunk toolhelp win32)
 @ stdcall SearchPathA(str str str long ptr ptr) SearchPathA
 @ stdcall SearchPathW(wstr wstr wstr long ptr ptr) SearchPathW
 @ stdcall SetCommBreak(long) SetCommBreak
-@ stdcall SetCommConfig(long ptr) SetCommConfig
+@ stdcall SetCommConfig(long ptr long) SetCommConfig
 @ stdcall SetCommMask(long ptr) SetCommMask
 @ stdcall SetCommState(long ptr) SetCommState
 @ stdcall SetCommTimeouts(long ptr) SetCommTimeouts

include/winbase.h

@@ -1546,7 +1546,7 @@ BOOL        WINAPI RevertToSelf(void);
 DWORD       WINAPI SearchPathA(LPCSTR,LPCSTR,LPCSTR,DWORD,LPSTR,LPSTR*);
 DWORD       WINAPI SearchPathW(LPCWSTR,LPCWSTR,LPCWSTR,DWORD,LPWSTR,LPWSTR*);
 #define     SearchPath WINELIB_NAME_AW(SearchPath)
-BOOL        WINAPI SetCommConfig(HANDLE,LPCOMMCONFIG);
+BOOL        WINAPI SetCommConfig(HANDLE,LPCOMMCONFIG,DWORD);
 BOOL        WINAPI SetCommBreak(HANDLE);
 BOOL        WINAPI SetCommMask(HANDLE,DWORD);
 BOOL        WINAPI SetCommState(HANDLE,LPDCB);