gpio: check request result

Make sure the pin request passed before attempting to use it later on.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/cmd_gpio.c b/common/cmd_gpio.c
index 9c9de28..9cc790a 100644
--- a/common/cmd_gpio.c
+++ b/common/cmd_gpio.c
@@ -57,7 +57,10 @@
 		goto show_usage;
 
 	/* grab the pin before we tweak it */
-	gpio_request(gpio, "cmd_gpio");
+	if (gpio_request(gpio, "cmd_gpio")) {
+		printf("gpio: requesting pin %u failed\n", gpio);
+		return -1;
+	}
 
 	/* finally, let's do it: set direction and exec command */
 	if (sub_cmd == GPIO_INPUT) {