Messages in this thread | | | From | Andy Shevchenko <> | Date | Wed, 21 Mar 2018 19:45:29 +0200 | Subject | Re: [PATCH v3 3/8] gpio: pci-idio-16: Implement get_multiple callback |
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On Sat, Mar 17, 2018 at 5:50 PM, William Breathitt Gray <vilhelm.gray@gmail.com> 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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