From: David Laight <david.laight.linux@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>,
Yury Norov <yury.norov@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
Geert Uytterhoeven <geert+renesas@glider.be>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Crt Mori <cmo@melexis.com>,
Richard Genoud <richard.genoud@bootlin.com>,
Luo Jie <quic_luoj@quicinc.com>,
Peter Zijlstra <peterz@infradead.org>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org, "David S . Miller" <davem@davemloft.net>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Andreas Noever <andreas.noever@gmail.com>,
Yehezkel Bernat <YehezkelShB@gmail.com>,
Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Subject: Re: [PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG()
Date: Sun, 28 Dec 2025 22:50:04 +0000 [thread overview]
Message-ID: <20251228225004.69a6972f@pumpkin> (raw)
In-Reply-To: <aVF8uQxjz9trZAHY@smile.fi.intel.com>
On Sun, 28 Dec 2025 20:53:45 +0200
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:
> On Wed, Dec 17, 2025 at 10:31:55PM +0000, David Laight wrote:
> > On Wed, 17 Dec 2025 10:26:18 +0000
> > Jonathan Cameron <jonathan.cameron@huawei.com> wrote:
> > > On Fri, 12 Dec 2025 19:37:13 +0000
> > > david.laight.linux@gmail.com wrote:
>
> ...
>
> > > > + BUILD_BUG_ON_MSG((mask) + 0U + 0UL + 0ULL > \
> > > > + ~0ULL >> (64 - 8 * sizeof (reg)), \
> > >
> > > Trivial. sizeof(reg) is much more comment syntax in kernel code.
> > (common)
> >
> > Hmm. sizeof is an operator not a function.
> > Its argument is either a variable/expression or a bracketed type
> > (I don't usually put variables in brackets).
> > So 'sizeof(reg)' is nearly as bad as 'return(reg)'.
>
> Yet, it's a style used de facto in the Linux kernel. I am with Jonathan on this.
Not hard to change :-)
There is a more interesting question as to whether that check is
needed at all?
It is only really the sanity checks (and the fact that __builtin_ffs() is
sub-optimal) that stop the functions being 'reasonable' for non-constant
values.
David
next prev parent reply other threads:[~2025-12-28 22:50 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-12 19:37 [PATCH v2 0/16] bitfield: tidy up bitfield.h david.laight.linux
2025-12-12 19:37 ` [PATCH v2 01/16] nfp: Call FIELD_PREP() in NFP_ETH_SET_BIT_CONFIG() wrapper david.laight.linux
2025-12-12 23:10 ` Jakub Kicinski
2025-12-12 19:37 ` [PATCH v2 02/16] thunderbolt: Don't pass a bitfield to FIELD_GET david.laight.linux
2025-12-13 2:28 ` Yury Norov
2025-12-13 10:01 ` David Laight
2025-12-13 22:14 ` David Laight
2025-12-12 19:37 ` [PATCH v2 03/16] bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16() david.laight.linux
2025-12-17 13:22 ` Nicolas Frattaroli
2025-12-18 0:16 ` Yury Norov
2025-12-18 8:44 ` David Laight
2025-12-19 13:11 ` Nicolas Frattaroli
2026-01-21 16:50 ` Geert Uytterhoeven
2026-01-21 16:52 ` Geert Uytterhoeven
2026-01-21 18:59 ` David Laight
2025-12-12 19:37 ` [PATCH v2 04/16] bitfield: Copy #define parameters to locals david.laight.linux
2025-12-12 19:37 ` [PATCH v2 05/16] bitfield: Merge __field_prep/get() into field_prep/get() david.laight.linux
2025-12-12 19:37 ` [PATCH v2 06/16] bitfield: Remove some pointless casts david.laight.linux
2025-12-12 19:37 ` [PATCH v2 07/16] bitfield: FIELD_MODIFY: Only do a single read/write on the target david.laight.linux
2025-12-12 19:37 ` [PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG() david.laight.linux
2025-12-17 10:26 ` Jonathan Cameron
2025-12-17 22:31 ` David Laight
2025-12-18 0:10 ` Yury Norov
2025-12-28 18:53 ` Andy Shevchenko
2025-12-28 22:50 ` David Laight [this message]
2025-12-12 19:37 ` [PATCH v2 09/16] bitfield: Rename __FIELD_PREP/GET() to __BF_FIELD_PREP/GET() david.laight.linux
2025-12-12 19:37 ` [PATCH v2 10/16] bitfield: Split the 'val' check out of __BF_FIELD_CHECK_MASK() david.laight.linux
2025-12-12 19:37 ` [PATCH v2 11/16] bitfield: Common up validation of the mask parameter david.laight.linux
2025-12-14 6:19 ` kernel test robot
2025-12-14 13:17 ` David Laight
2025-12-12 19:37 ` [PATCH v2 12/16] bitfield: Remove leading _ from #define formal parameter names david.laight.linux
2025-12-12 19:37 ` [PATCH v2 13/16] bitfield: Reduce indentation david.laight.linux
2025-12-12 19:37 ` [PATCH v2 14/16] bitfield: Add comment block for the host/fixed endian functions david.laight.linux
2025-12-12 19:37 ` [PATCH v2 15/16] bitfield: Update comments for le/be functions david.laight.linux
2025-12-12 19:37 ` [PATCH v2 16/16] build_bug.h; Remove __BUILD_BUG_ON_NOT_POWER_OF_2() david.laight.linux
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