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    Subject[PATCH v4 6/7] gpio: gpio-mm: Implement get_multiple callback
    Date
    The Diamond Systems GPIO-MM series of devices contain two 82C55A
    devices, which each feature three 8-bit ports of I/O. Since eight input
    lines are acquired on a single port input read, the GPIO-MM GPIO driver
    may improve multiple input reads by utilizing a get_multiple callback.
    This patch implements the gpiomm_gpio_get_multiple function which serves
    as the respective get_multiple callback.

    Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
    ---
    drivers/gpio/gpio-gpio-mm.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
    1 file changed, 47 insertions(+)

    diff --git a/drivers/gpio/gpio-gpio-mm.c b/drivers/gpio/gpio-gpio-mm.c
    index 11ade5b288f8..d496cc56c2a2 100644
    --- a/drivers/gpio/gpio-gpio-mm.c
    +++ b/drivers/gpio/gpio-gpio-mm.c
    @@ -14,6 +14,7 @@
    * This driver supports the following Diamond Systems devices: GPIO-MM and
    * GPIO-MM-12.
    */
    +#include <linux/bitmap.h>
    #include <linux/bitops.h>
    #include <linux/device.h>
    #include <linux/errno.h>
    @@ -171,6 +172,51 @@ static int gpiomm_gpio_get(struct gpio_chip *chip, unsigned int offset)
    return !!(port_state & mask);
    }

    +static int gpiomm_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
    + unsigned long *bits)
    +{
    + struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
    + size_t i;
    + const size_t ports[] = { 0, 1, 2, 4, 5, 6 };
    + 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;
    +
    + /* 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 = inb(gpiommgpio->base + ports[i]);
    +
    + /* store acquired bits at respective bits array offset */
    + bits[word_index] |= port_state << word_offset;
    + }
    +
    + return 0;
    +}
    +
    static void gpiomm_gpio_set(struct gpio_chip *chip, unsigned int offset,
    int value)
    {
    @@ -268,6 +314,7 @@ static int gpiomm_probe(struct device *dev, unsigned int id)
    gpiommgpio->chip.direction_input = gpiomm_gpio_direction_input;
    gpiommgpio->chip.direction_output = gpiomm_gpio_direction_output;
    gpiommgpio->chip.get = gpiomm_gpio_get;
    + gpiommgpio->chip.get_multiple = gpiomm_gpio_get_multiple;
    gpiommgpio->chip.set = gpiomm_gpio_set;
    gpiommgpio->chip.set_multiple = gpiomm_gpio_set_multiple;
    gpiommgpio->base = base[id];
    --
    2.16.2
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