On Tue, Oct 02, 2018 at 09:00:45AM +0200, Rasmus Villemoes wrote:
> On 2018-10-02 03:14, William Breathitt Gray wrote:
> > /* 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 */
> > + for_each_set_clump(i, word, offset, mask, ARRAY_SIZE(ports), 8) {
> > port_state = inb(dio48egpio->base + ports[i]);
> > -
> > - /* store acquired bits at respective bits array offset */
> > - bits[word_index] |= port_state << word_offset;
> > + bits[word] |= port_state << offset;
>
> Somewhat unrelated to this series, but is the existing code correct? I'd
> expect the RHS to be masked by word_mask; otherwise we might set bits in
> bits[] that were not requested? And if one does that, the !word_mask
> test is merely an optimization to avoid reading the gpios when the
> result would be ignored anyway. Perhaps no caller cares.
>
> Rasmus
I don't think the caller cares in this case. Take a look at the
gpiod_get_array_value_complex function: the desired inputs are collected
before gpio_chip_get_multiple is called and then looped through after --
unrequested bits are simply ignored.
This caller behavior also makes sense because a bit value of 0 in the
bits array does not necessarily mean the input was not requested, but
may instead mean that the value at the input is 0; therefore, the caller
must keep track of the requested inputs rather than try to deduce them
from the values in the bits array.
William Breathitt Gray
