On Tue, Mar 13, 2018 at 06:04:33PM +0200, Andy Shevchenko wrote:
>On Mon, Mar 12, 2018 at 10:49 PM, William Breathitt Gray
><vilhelm.gray@xxxxxxxxx> wrote:
>
>> +static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
>> + unsigned long *mask, unsigned long *bits)
>> +{
>
>
>> + /* clear bits array to a clean slate */
>> + for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
>> + bits[i / BITS_PER_LONG] = 0;
>
>bitmap_clear() or bitmap_zero()
bitmap_zero() would be perfect for this situation. I'll submit a version
2 of this patchset with this change for the various drivers herein.
>
>> + /* 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;
>> + }
>
>for_each_set_bit() ?
>
>> + /* store acquired bits */
>> + bits[BIT_WORD(i)] |= port_state << bit_word_offset;
>
>__set_bit()
>__clear_bit()
I'm not sure for_each_set_bit() and __set_bit()/__clear_bit() would be
good for this particular situation since I'm working with the entire
register word (8 bits for this specific device) at a time.
Since I know each register word is 8-bits, I can make 8-bit jumps and
skips rather than evaluating each bit individually. Similarly, it seems
more efficient to store the input 8 bits at a time rather than breaking
it up to individual bits.
However, I do see how all these inline bitwise operations could make it
difficult to follow the code, so perhaps I can break it up across more
lines so that the logic of the loop becomes easier to read.
William Breathitt Gray
>
>We have bitmap API for *ages*. Is it too hard to check?
>
>--
>With Best Regards,
>Andy Shevchenko
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