cmd: pwm: Rework argc sanity checking

Currently, we check argc in a number of places to make sure that we have
all of the required arguments for each of the pwm sub-commands.
However, there's at least one place where we've got dead code as we'll
never have argc == 0, due to checking that argc was at least 4 earlier
and having only subtracted 3.  Rework things so that when we have
determined our subcommand make sure we have the right number of
arguments for it, or error out.  This means we can stop checking against
argc again later.

Reported-by: Coverity (CID: 316601)
Cc: Pragnesh Patel <pragnesh.patel@sifive.com>
Signed-off-by: Tom Rini <trini@konsulko.com>

cmd/pwm.c

@@ -34,11 +34,9 @@ static int do_pwm(struct cmd_tbl *cmdtp, int flag, int argc,
 	argc -= 2;
 	argv += 2;
 
-	if (argc > 0) {
-		str_pwm = *argv;
-		argc--;
-		argv++;
-	}
+	str_pwm = *argv;
+	argc--;
+	argv++;
 
 	if (!str_pwm)
 		return CMD_RET_USAGE;
@@ -46,15 +44,23 @@ static int do_pwm(struct cmd_tbl *cmdtp, int flag, int argc,
 	switch (*str_cmd) {
 	case 'i':
 		sub_cmd = PWM_SET_INVERT;
+		if (argc != 2)
+			return CMD_RET_USAGE;
 		break;
 	case 'c':
 		sub_cmd = PWM_SET_CONFIG;
+		if (argc != 3)
+			return CMD_RET_USAGE;
 		break;
 	case 'e':
 		sub_cmd = PWM_SET_ENABLE;
+		if (argc != 1)
+			return CMD_RET_USAGE;
 		break;
 	case 'd':
 		sub_cmd = PWM_SET_DISABLE;
+		if (argc != 1)
+			return CMD_RET_USAGE;
 		break;
 	default:
 		return CMD_RET_USAGE;
@@ -67,38 +73,29 @@ static int do_pwm(struct cmd_tbl *cmdtp, int flag, int argc,
 		return cmd_process_error(cmdtp, ret);
 	}
 
-	if (argc > 0) {
-		str_channel = *argv;
-		channel = simple_strtoul(str_channel, NULL, 10);
-		argc--;
-		argv++;
-	} else {
-		return CMD_RET_USAGE;
-	}
+	str_channel = *argv;
+	channel = simple_strtoul(str_channel, NULL, 10);
+	argc--;
+	argv++;
 
-	if (sub_cmd == PWM_SET_INVERT && argc > 0) {
+	if (sub_cmd == PWM_SET_INVERT) {
 		str_enable = *argv;
 		pwm_enable = simple_strtoul(str_enable, NULL, 10);
 		ret = pwm_set_invert(dev, channel, pwm_enable);
-	} else if (sub_cmd == PWM_SET_CONFIG && argc == 2) {
+	} else if (sub_cmd == PWM_SET_CONFIG) {
 		str_period = *argv;
 		argc--;
 		argv++;
 		period_ns = simple_strtoul(str_period, NULL, 10);
 
-		if (argc > 0) {
-			str_duty = *argv;
-			duty_ns = simple_strtoul(str_duty, NULL, 10);
-		}
+		str_duty = *argv;
+		duty_ns = simple_strtoul(str_duty, NULL, 10);
 
 		ret = pwm_set_config(dev, channel, period_ns, duty_ns);
 	} else if (sub_cmd == PWM_SET_ENABLE) {
 		ret = pwm_set_enable(dev, channel, 1);
 	} else if (sub_cmd == PWM_SET_DISABLE) {
 		ret = pwm_set_enable(dev, channel, 0);
-	} else {
-		printf("PWM arguments missing\n");
-		return CMD_RET_FAILURE;
 	}
 
 	if (ret) {