Re: [PATCH 2/3] linux/bits.h: Add fixed-width GENMASK and BIT macros

Andy Shevchenko
2023-06-20T14:55:29Z

On Tue, Jun 20, 2023 at 05:47:34PM +0300, Jani Nikula wrote:
> On Thu, 15 Jun 2023, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> > On Fri, May 12, 2023 at 02:45:19PM +0300, Jani Nikula wrote:
> >> On Fri, 12 May 2023, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> >> > On Fri, May 12, 2023 at 02:25:18PM +0300, Jani Nikula wrote:
> >> >> On Fri, 12 May 2023, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> >> >> > On Mon, May 08, 2023 at 10:14:02PM -0700, Lucas De Marchi wrote:
> >> >> >> Add GENMASK_U32(), GENMASK_U16() and GENMASK_U8() macros to create
> >> >> >> masks for fixed-width types and also the corresponding BIT_U32(),
> >> >> >> BIT_U16() and BIT_U8().
> >> >> >
> >> >> > Why?
> >> >>
> >> >> The main reason is that GENMASK() and BIT() size varies for 32/64 bit
> >> >> builds.
> >> >
> >> > When needed GENMASK_ULL() can be used (with respective castings perhaps)
> >> > and BIT_ULL(), no?
> >>
> >> How does that help with making them the same 32-bit size on both 32 and
> >> 64 bit builds?
> >
> > u32 x = GENMASK();
> > u64 y = GENMASK_ULL();
> >
> > No? Then use in your code either x or y. Note that I assume that the parameters
> > to GENMASK*() are built-time constants. Is it the case for you?
>
> What's wrong with wanting to define macros with specific size, depending
> on e.g. hardware registers instead of build size?

Nothing, but I think the problem is smaller than it's presented.
And there are already header for bitfields with a lot of helpers
for (similar) cases if not yours.

> What would you use for printk format if you wanted to to print
> GENMASK()?

%lu, no?

--
With Best Regards,
Andy Shevchenko