[DRIVER] fxl6408: add reset-gpios control with shared line support

Add optional reset-gpios pin control.
Also, some systems connect several devices to a single reset GPIO.
For these devices to get out of reset and probe successfully, treat
the reset returning -EBUSY as the line already having been hogged
and do not abort the probe.

drivers/gpio/gpio-fxl6408.c

@@ -154,10 +154,23 @@ static int fxl6408_probe(struct i2c_client *client,
 	struct device *dev = &client->dev;
 	struct fxl6408_chip *chip;
 	struct gpio_chip *gc;
+	struct gpio_desc *reset_gpio;
 	unsigned int val;
+	int gpio_base;
 	int ret;
 	u8 device_id;
 
+	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio)) {
+		ret = PTR_ERR(reset_gpio);
+		/* reset may be shared with other devices: do not abort on -EBUSY */
+		if (ret != -EBUSY) {
+			dev_err(dev, "Could not get reset-gpios: %d\n", ret);
+			return ret;
+		}
+		dev_warn(dev, "Could not get reset-gpios: already in use\n", ret);
+	}
+
 	/* Check the device ID register to see if it's responding.
 	 * This also clears RST_INT as a side effect, so we won't get
 	 * the "we've been power cycled" interrupt once we enable