gpio: 104-idio-16: Implement get_multiple callback

The ACCES I/O 104-IDIO-16 series of devices provides 16
optically-isolated digital inputs accessed via two 8-bit ports. Since
eight input lines are acquired on a single port input read, the
104-IDIO-16 GPIO driver may improve multiple input reads by utilizing a
get_multiple callback. This patch implements the
idio_16_gpio_get_multiple function which serves as the respective
get_multiple callback.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-104-idio-16.c

@@ -90,6 +90,20 @@ static int idio_16_gpio_get(struct gpio_chip *chip, unsigned offset)
 	return !!(inb(idio16gpio->base + 5) & (mask>>8));
 }
 
+static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
+
+	*bits = 0;
+	if (*mask & GENMASK(23, 16))
+		*bits |= (unsigned long)inb(idio16gpio->base + 1) << 16;
+	if (*mask & GENMASK(31, 24))
+		*bits |= (unsigned long)inb(idio16gpio->base + 5) << 24;
+
+	return 0;
+}
+
 static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 {
 	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
@@ -244,6 +258,7 @@ static int idio_16_probe(struct device *dev, unsigned int id)
 	idio16gpio->chip.direction_input = idio_16_gpio_direction_input;
 	idio16gpio->chip.direction_output = idio_16_gpio_direction_output;
 	idio16gpio->chip.get = idio_16_gpio_get;
+	idio16gpio->chip.get_multiple = idio_16_gpio_get_multiple;
 	idio16gpio->chip.set = idio_16_gpio_set;
 	idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;
 	idio16gpio->base = base[id];