setexpr: simplify code, improve help message

Simplify the argument checking for the "setexpr" command.  This is
done mainly to make future extensions easier.

Also improve the help message for the one argument version of the
command - this does not "load an address", but a value, which in
this context may be a plain number or a pointer dereference.

Signed-off-by: Wolfgang Denk <wd@denx.de>

common/cmd_setexpr.c

@@ -56,22 +56,26 @@ static int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	ulong value;
 	int w;
 
-	/* Validate arguments */
-	if (argc != 5 && argc != 3)
-		return CMD_RET_USAGE;
-	if (argc == 5 && strlen(argv[3]) != 1)
+	if (argc < 3)
 		return CMD_RET_USAGE;
 
 	w = cmd_get_data_size(argv[0], 4);
 
 	a = get_arg(argv[2], w);
 
+	/* plain assignment: "setexpr name value" */
 	if (argc == 3) {
 		setenv_hex(argv[1], a);
-
 		return 0;
 	}
 
+	/* standard operators: "setexpr name val1 op val2" */
+	if (argc != 5)
+		return CMD_RET_USAGE;
+
+	if (strlen(argv[3]) != 1)
+		return CMD_RET_USAGE;
+
 	b = get_arg(argv[4], w);
 
 	switch (argv[3][0]) {
@@ -117,6 +121,6 @@ U_BOOT_CMD(
 	"      express specified by <op>.  <op> can be &, |, ^, +, -, *, /, %\n"
 	"      size argument is only meaningful if value1 and/or value2 are\n"
 	"      memory addresses (*)\n"
-	"setexpr[.b, .w, .l] name *value\n"
-	"    - load a memory address into a variable"
+	"setexpr[.b, .w, .l] name [*]value\n"
+	"    - load a value into a variable"
 );