On Thu, Dec 9, 2021 at 9:26 AM Zev Weiss [off-list ref] wrote:

On Wed, Dec 08, 2021 at 05:58:30AM PST, Jonathan Neuschäfer wrote:

quoted

quoted

BIT()

I'll use it, but in this case, I think it doesn't simplify much the
whole expression all that much. Is there perhaps a macro that
constructs a continuous bitmask of N bits, perhaps additionally
left-shifted by M bits?

Maybe somewhere in the bitmap_* API...

There's GENMASK(), though it takes a high bit and low bit rather than a
bit position and count, so it'd require a small bit of arithmetic, e.g.

  lastbit = gpio->first_irq_bit + gpio->num_irqs - 1;
  ours = GENMASK(lastbit, gpio->first_irq_bit);

or a manual shift:

  ours = GENMASK(gpio->num_irqs - 1, 0) << gpio->first_irq_bit;

I think this can be handled with FIELD_PREP() from
<linux/bitfield.h>? Some examples at the top of the
header.

Yours,
Linus Walleij