linux-kernel - Re: [PATCH v6 12/26] bitfield: Add less-checking __FIELD

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Message-ID: <aQzIAd91tlR3o9hu@smile.fi.intel.com>
Date: Thu, 6 Nov 2025 18:08:33 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>,
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Subject: Re: [PATCH v6 12/26] bitfield: Add less-checking __FIELD_{GET,PREP}()

On Thu, Nov 06, 2025 at 11:01:39AM -0500, Yury Norov wrote:
> On Thu, Nov 06, 2025 at 04:44:31PM +0200, Andy Shevchenko wrote:
> > On Thu, Nov 06, 2025 at 02:34:00PM +0100, Geert Uytterhoeven wrote:
> > > The BUILD_BUG_ON_MSG() check against "~0ull" works only with "unsigned
> > > (long) long" _mask types.  For constant masks, that condition is usually
> > > met, as GENMASK() yields an UL value.  The few places where the
> > > constant mask is stored in an intermediate variable were fixed by
> > > changing the variable type to u64 (see e.g. [1] and [2]).
> > > 
> > > However, for non-constant masks, smaller unsigned types should be valid,
> > > too, but currently lead to "result of comparison of constant
> > > 18446744073709551615 with expression of type ... is always
> > > false"-warnings with clang and W=1.
> > > 
> > > Hence refactor the __BF_FIELD_CHECK() helper, and factor out
> > > __FIELD_{GET,PREP}().  The later lack the single problematic check, but
> > > are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
> > > used in the fully non-const variants later.
> > > 
> > > [1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
> > >     HWM_FIELD_PREP()")
> > > [2] commit cfd6fb45cfaf46fa ("crypto: ccree - avoid out-of-range
> > >     warnings from clang")
> > 
> > 
> > Also can be made as
> > 
> > Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
> > 
> > The positive effect that one may click that on Git Web.
> > Ideally, of course, would be an additional parses on Git Web kernel.org uses to
> > parse that standard "commit ...()" notation to add the respective HREF link.
> 
> Those flying over Atlantic or cruising cross Caribbean would disagree. :)

They won't. The purpose of these Links is described in the above commit message.
Even they read the commit message before clicking.

-- 
With Best Regards,
Andy Shevchenko