On Sat, Mar 17, 2018 at 5:50 PM, William Breathitt Gray
<vilhelm.gray@xxxxxxxxx> wrote:
> 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.
> +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, 0);
gpio_reg_size - 1?
Though I would prefer not to have that variable at all, just use 8 or
7 respectively.
> + unsigned long port_state;
> + u8 __iomem ports[] = {
> + idio16gpio->reg->out0_7, idio16gpio->reg->out8_15,
> + idio16gpio->reg->in0_7, idio16gpio->reg->in8_15
I would leave comma even here.
> + };
> + /* 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;
> + }
I would propose to do other way around, i.e.
read all ports to the bitmap array and call bitmap_and() after.
Further optimization can be something like introduction of generic
bitmap_copy_uXX_off(unsigned long *dst, u8 src, unsigned int offset);
It can be done using macros, though it's another story not quite
related to the topic.
> +}
--
With Best Regards,
Andy Shevchenko
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