The ACCES I/O 104-IDI-48 series of devices provides 48
optically-isolated inputs accessed via six 8-bit ports. Since eight
input lines are acquired on a single port input read, the 104-IDI-48
GPIO driver may improve multiple input reads by utilizing a get_multiple
callback. This patch implements the idi_48_gpio_get_multiple function
which serves as the respective get_multiple callback.

Signed-off-by: William Breathitt Gray <vilhelm.g...@gmail.com>
---
 drivers/gpio/gpio-104-idi-48.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/gpio/gpio-104-idi-48.c b/drivers/gpio/gpio-104-idi-48.c
index add859d59766..d82139c3117a 100644
--- a/drivers/gpio/gpio-104-idi-48.c
+++ b/drivers/gpio/gpio-104-idi-48.c
@@ -88,6 +88,46 @@ static int idi_48_gpio_get(struct gpio_chip *chip, unsigned 
offset)
        return 0;
 }
 
+static int idi_48_gpio_get_multiple(struct gpio_chip *chip, unsigned long 
*mask,
+       unsigned long *bits)
+{
+       struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
+       unsigned int i;
+       const unsigned int gpio_reg_size = 8;
+       unsigned int bit_word_offset;
+       unsigned int bits_mask;
+       const unsigned long reg_mask = GENMASK(gpio_reg_size, 0);
+       unsigned int port;
+       unsigned int in_port;
+       unsigned long port_state;
+
+       /* clear bits array to a clean slate */
+       for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
+               bits[i / BITS_PER_LONG] = 0;
+
+       /* get bits are evaluated a gpio register size at a time */
+       for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
+               bit_word_offset = i % BITS_PER_LONG;
+               bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
+               if (!bits_mask) {
+                       /* no get bits in this register so skip to next one */
+                       continue;
+               }
+
+               /* compute input port offset */
+               port = i / gpio_reg_size;
+               in_port = (port > 2) ? port + 1 : port;
+
+               /* get input bits */
+               port_state = inb(idi48gpio->base + in_port);
+
+               /* store acquired bits */
+               bits[BIT_WORD(i)] |= port_state << bit_word_offset;
+       }
+
+       return 0;
+}
+
 static void idi_48_irq_ack(struct irq_data *data)
 {
 }
@@ -256,6 +296,7 @@ static int idi_48_probe(struct device *dev, unsigned int id)
        idi48gpio->chip.get_direction = idi_48_gpio_get_direction;
        idi48gpio->chip.direction_input = idi_48_gpio_direction_input;
        idi48gpio->chip.get = idi_48_gpio_get;
+       idi48gpio->chip.get_multiple = idi_48_gpio_get_multiple;
        idi48gpio->base = base[id];
 
        raw_spin_lock_init(&idi48gpio->lock);
-- 
2.16.2

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