gpio: pci-idio-16: Implement get_multiple callback

The ACCES I/O PCI-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
PCI-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>

diff --git a/drivers/gpio/gpio-pci-idio-16.c b/drivers/gpio/gpio-pci-idio-16.c
index 57d1b7fbf07b6035ae20be08791acb1f7e6fd02e..1948724d8c369df7baab3e889138408c1e860db8 100644 (file)
--- a/drivers/gpio/gpio-pci-idio-16.c
+++ b/drivers/gpio/gpio-pci-idio-16.c
@@ -11,6 +11,7 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  */
+#include <linux/bitmap.h>
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/errno.h>
@@ -103,6 +104,54 @@ static int idio_16_gpio_get(struct gpio_chip *chip, unsigned int offset)
        return !!(ioread8(&idio16gpio->reg->in8_15) & (mask >> 24));
 }
 
+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);
+       size_t i;
+       const unsigned int gpio_reg_size = 8;
+       unsigned int bits_offset;
+       size_t word_index;
+       unsigned int word_offset;
+       unsigned long word_mask;
+       const unsigned long port_mask = GENMASK(gpio_reg_size - 1, 0);
+       unsigned long port_state;
+       u8 __iomem ports[] = {
+               idio16gpio->reg->out0_7, idio16gpio->reg->out8_15,
+               idio16gpio->reg->in0_7, idio16gpio->reg->in8_15,
+       };
+
+       /* clear bits array to a clean slate */
+       bitmap_zero(bits, chip->ngpio);
+
+       /* get bits are evaluated a gpio port register at a time */
+       for (i = 0; i < ARRAY_SIZE(ports); i++) {
+               /* gpio offset in bits array */
+               bits_offset = i * gpio_reg_size;
+
+               /* word index for bits array */
+               word_index = BIT_WORD(bits_offset);
+
+               /* gpio offset within current word of bits array */
+               word_offset = bits_offset % BITS_PER_LONG;
+
+               /* mask of get bits for current gpio within current word */
+               word_mask = mask[word_index] & (port_mask << word_offset);
+               if (!word_mask) {
+                       /* no get bits in this port so skip to next one */
+                       continue;
+               }
+
+               /* read bits from current gpio port */
+               port_state = ioread8(ports + i);
+
+               /* store acquired bits at respective bits array offset */
+               bits[word_index] |= port_state << word_offset;
+       }
+
+       return 0;
+}
+
 static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
        int value)
 {
@@ -299,6 +348,7 @@ static int idio_16_probe(struct pci_dev *pdev, const struct pci_device_id *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;