Input: gpio_keys - don't report events on gpio failure

In the cases where the gpio chip fails to acquire the current state an
error is reported back to gpio_keys. This is currently interpreted as if
the line went high, which just confuses the developer.

This patch introduces an error print in this case and skipps the
reporting of a input event; to aid in debugging this issue.
Reported-by: NJohn Stultz <john.stultz@linaro.org>
Signed-off-by: NBjorn Andersson <bjorn.andersson@sonymobile.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/gpio_keys.c

@@ -341,8 +341,14 @@ static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata)
 	const struct gpio_keys_button *button = bdata->button;
 	struct input_dev *input = bdata->input;
 	unsigned int type = button->type ?: EV_KEY;
-	int state = (gpio_get_value_cansleep(button->gpio) ? 1 : 0) ^ button->active_low;
+	int state = gpio_get_value_cansleep(button->gpio);
 
+	if (state < 0) {
+		dev_err(input->dev.parent, "failed to get gpio state\n");
+		return;
+	}
+
+	state = (state ? 1 : 0) ^ button->active_low;
 	if (type == EV_ABS) {
 		if (state)
 			input_event(input, type, button->code, button->value);