USB: serial: cp210x: provide gpio valid mask

Use the new GPIO valid-mask feature to inform gpiolib which pins are
available for use instead of handling that in a request callback.

This also allows user space to figure out which pins are available
through the chardev interface without having to request each pin in
turn.

Note that the return value when requesting an unavailable pin will now
be -EINVAL instead of -ENODEV.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/cp210x.c

@@ -1410,17 +1410,6 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state)
 }
 
 #ifdef CONFIG_GPIOLIB
-static int cp210x_gpio_request(struct gpio_chip *gc, unsigned int offset)
-{
-	struct usb_serial *serial = gpiochip_get_data(gc);
-	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
-
-	if (priv->gpio_altfunc & BIT(offset))
-		return -ENODEV;
-
-	return 0;
-}
-
 static int cp210x_gpio_get(struct gpio_chip *gc, unsigned int gpio)
 {
 	struct usb_serial *serial = gpiochip_get_data(gc);
@@ -1549,6 +1538,18 @@ static int cp210x_gpio_set_config(struct gpio_chip *gc, unsigned int gpio,
 	return -ENOTSUPP;
 }
 
+static int cp210x_gpio_init_valid_mask(struct gpio_chip *gc,
+		unsigned long *valid_mask, unsigned int ngpios)
+{
+	struct usb_serial *serial = gpiochip_get_data(gc);
+	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
+	unsigned long altfunc_mask = priv->gpio_altfunc;
+
+	bitmap_complement(valid_mask, &altfunc_mask, ngpios);
+
+	return 0;
+}
+
 /*
  * This function is for configuring GPIO using shared pins, where other signals
  * are made unavailable by configuring the use of GPIO. This is believed to be
@@ -1786,13 +1787,13 @@ static int cp210x_gpio_init(struct usb_serial *serial)
 		return result;
 
 	priv->gc.label = "cp210x";
-	priv->gc.request = cp210x_gpio_request;
 	priv->gc.get_direction = cp210x_gpio_direction_get;
 	priv->gc.direction_input = cp210x_gpio_direction_input;
 	priv->gc.direction_output = cp210x_gpio_direction_output;
 	priv->gc.get = cp210x_gpio_get;
 	priv->gc.set = cp210x_gpio_set;
 	priv->gc.set_config = cp210x_gpio_set_config;
+	priv->gc.init_valid_mask = cp210x_gpio_init_valid_mask;
 	priv->gc.owner = THIS_MODULE;
 	priv->gc.parent = &serial->interface->dev;
 	priv->gc.base = -1;