Add getenv_hex() to return an environment variable as hex

This conversion is required in a number of places in U-Boot. Add a
standard function to provide this feature, so we avoid all the different
variations in the way it is coded.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/cmd_nvedit.c

@@ -315,6 +315,21 @@ int setenv_hex(const char *varname, ulong value)
 	return setenv(varname, str);
 }
 
+ulong getenv_hex(const char *varname, ulong default_val)
+{
+	const char *s;
+	ulong value;
+	char *endp;
+
+	s = getenv(varname);
+	if (s)
+		value = simple_strtoul(s, &endp, 16);
+	if (!s || endp == s)
+		return default_val;
+
+	return value;
+}
+
 #ifndef CONFIG_SPL_BUILD
 static int do_env_set(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {

include/common.h

@@ -352,6 +352,19 @@ int	envmatch     (uchar *, int);
 char	*getenv	     (const char *);
 int	getenv_f     (const char *name, char *buf, unsigned len);
 ulong getenv_ulong(const char *name, int base, ulong default_val);
+
+/**
+ * getenv_hex() - Return an environment variable as a hex value
+ *
+ * Decode an environment as a hex number (it may or may not have a 0x
+ * prefix). If the environment variable cannot be found, or does not start
+ * with hex digits, the default value is returned.
+ *
+ * @varname:		Variable to decode
+ * @default_val:	Value to return on error
+ */
+ulong getenv_hex(const char *varname, ulong default_val);
+
 /*
  * Read an environment variable as a boolean
  * Return -1 if variable does not exist (default to true)