From: david.laight.linux@gmail.com
To: 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>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Crt Mori <cmo@melexis.com>,
Richard Genoud <richard.genoud@bootlin.com>,
Andy Shevchenko <andriy.shevchenko@intel.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>
Cc: David Laight <david.laight.linux@gmail.com>
Subject: [PATCH v2 07/16] bitfield: FIELD_MODIFY: Only do a single read/write on the target
Date: Fri, 12 Dec 2025 19:37:12 +0000 [thread overview]
Message-ID: <20251212193721.740055-8-david.laight.linux@gmail.com> (raw)
In-Reply-To: <20251212193721.740055-1-david.laight.linux@gmail.com>
From: David Laight <david.laight.linux@gmail.com>
Replace the:
*reg &= ~mask; *reg |= new_value;
with a single assignment.
While the compiler will usually optimise the extra access away
it isn't guaranteed.
Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
include/linux/bitfield.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index f1859e28df5d..c354ca2ef1a0 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -200,8 +200,7 @@
__auto_type _val = 1 ? (val) : _mask; \
typecheck_pointer(_reg_p); \
__BF_FIELD_CHECK(_mask, *(_reg_p), _val, "FIELD_MODIFY: "); \
- *(_reg_p) &= ~(_mask); \
- *(_reg_p) |= (_val << __bf_shf(_mask)) & _mask; \
+ *_reg_p = (*_reg_p & ~_mask) | ((_val << __bf_shf(_mask)) & _mask); \
})
extern void __compiletime_error("value doesn't fit into mask")
--
2.39.5
next prev parent reply other threads:[~2025-12-12 19:38 UTC|newest]
Thread overview: 23+ 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
2025-12-12 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 ` david.laight.linux [this message]
2025-12-12 19:37 ` [PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG() david.laight.linux
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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