Re: [PATCH v17 01/14] bitops: Introduce the for_each_set_clump8 macro

From: Geert Uytterhoeven
Date: Wed Oct 09 2019 - 14:54:20 EST

Hi Andy,

On Wed, Oct 9, 2019 at 7:09 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> On Thu, Oct 10, 2019 at 01:28:08AM +0900, Masahiro Yamada wrote:
> > On Thu, Oct 10, 2019 at 12:27 AM William Breathitt Gray
> > <vilhelm.gray@xxxxxxxxx> wrote:
> > >
> > > This macro iterates for each 8-bit group of bits (clump) with set bits,
> > > within a bitmap memory region. For each iteration, "start" is set to the
> > > bit offset of the found clump, while the respective clump value is
> > > stored to the location pointed by "clump". Additionally, the
> > > bitmap_get_value8 and bitmap_set_value8 functions are introduced to
> > > respectively get and set an 8-bit value in a bitmap memory region.
> > Why is the return type "unsigned long" where you know
> > it return the 8-bit value ?
> Because bitmap API operates on unsigned long type. This is not only
> consistency, but for sake of flexibility in case we would like to introduce
> more calls like clump16 or so.

TBH, that doesn't convince me: those functions explicitly take/return an
8-bit value, and have "8" in their name. The 8-bit value is never
really related to, retrieved from, or stored in a full "unsigned long"
element of a bitmap, only to/from/in a part (byte) of it.

Following your rationale, all of iowrite{8,16,32,64}*() should take an
"unsigned long" value, too.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds