arm: smh: Use numeric modes for smh_open

There's no point in using string constants for smh_open if we are just
going to have to parse them. Instead, use numeric modes. The user needs
to be a bit careful with these, since they are much closer semantically
to string modes used by fopen(3) than the numeric modes used with
open(2).

Signed-off-by: Sean Anderson <sean.anderson@seco.com>

include/semihosting.h

@@ -6,7 +6,30 @@
 #ifndef _SEMIHOSTING_H
 #define _SEMIHOSTING_H
 
-long smh_open(const char *fname, char *modestr);
+/**
+ * enum smh_open_mode - Numeric file modes for use with smh_open()
+ * MODE_READ: 'r'
+ * MODE_BINARY: 'b'
+ * MODE_PLUS: '+'
+ * MODE_WRITE: 'w'
+ * MODE_APPEND: 'a'
+ *
+ * These modes represent the mode string used by fopen(3) in a form which can
+ * be passed to smh_open(). These do NOT correspond directly to %O_RDONLY,
+ * %O_CREAT, etc; see fopen(3) for details. In particular, @MODE_PLUS
+ * effectively results in adding %O_RDWR, and @MODE_WRITE will add %O_TRUNC.
+ * For compatibility, @MODE_BINARY should be added when opening non-text files
+ * (such as images).
+ */
+enum smh_open_mode {
+	MODE_READ	= 0x0,
+	MODE_BINARY	= 0x1,
+	MODE_PLUS	= 0x2,
+	MODE_WRITE	= 0x4,
+	MODE_APPEND	= 0x8,
+};
+
+long smh_open(const char *fname, enum smh_open_mode mode);
 long smh_read(long fd, void *memp, size_t len);
 long smh_close(long fd);
 long smh_flen(long fd);