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Rozycki" , Thomas Bogendoerfer , Madhavan Srinivasan , Michael Ellerman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Chris Zankel , Max Filippov , Patrik Jakobsson , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Robin Murphy , Joerg Roedel , Will Deacon , Jakub Kicinski , Andrew Lunn , "David S. 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Let's make it part of the standard bitops > arsenal. > > Define the macro in a separate header file included from , > to allow using it in very low-level header files that may not want to > include all of . Nice catch. Thanks! > > Signed-off-by: Petr Tesarik > --- > MAINTAINERS | 1 + > include/linux/bitops.h | 1 + > include/linux/ffs_val.h | 21 +++++++++++++++++++++ > 3 files changed, 23 insertions(+) > create mode 100644 include/linux/ffs_val.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index a0dd762f5648b..8f15c76a67ea2 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -4466,6 +4466,7 @@ F: arch/*/lib/bitops.c > F: include/asm-generic/bitops > F: include/asm-generic/bitops.h > F: include/linux/bitops.h > +F: include/linux/ffs_val.h No need for a separate header. Just put int straight in bitops.h. > F: lib/hweight.c > F: lib/test_bitops.c > F: tools/*/bitops* > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > index ea7898cc59039..209f0c3e07b9e 100644 > --- a/include/linux/bitops.h > +++ b/include/linux/bitops.h > @@ -4,6 +4,7 @@ > > #include > #include > +#include > #include > > #include > diff --git a/include/linux/ffs_val.h b/include/linux/ffs_val.h > new file mode 100644 > index 0000000000000..193ec86d2b53b > --- /dev/null > +++ b/include/linux/ffs_val.h > @@ -0,0 +1,21 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ASM_LINUX_FFS_VAL_H_ > +#define _ASM_LINUX_FFS_VAL_H_ > + > +/** > + * ffs_val - find the value of the first set bit By definition, the value of 1st set bit is 1, just like any other set bit. :) > + * @x: the value to search > + * > + * Unlike ffs(), which returns a bit position, ffs_val() returns the bit > + * value itself. > + * > + * Returns: > + * least significant non-zero bit, 0 if all bits are zero > + */ > +#define ffs_val(x) \ > +({ \ > + const typeof(x) val__ = (x); \ const auto? Also, are you sure it works OK with unsigned types? No warnings? Maybe add a test? > + val__ & -val__; \ > +}) This macro returns in fact a mask containing LSB only, so I'd suggest to choose a name like lsb_mask(). This is also a replacement of BIT(ffs()), GENMASK(ffs(), 0) constructions. Can you check the kernel, and convert those patterns too? I found at least one in drivers/clk/nxp/clk-lpc32xx.c:lpc32xx_clk_div_quirk(). Thanks, Yury > + > +#endif /* _ASM_LINUX_FFS_VAL_H_ */ > -- > 2.52.0