17 Jul, 2019
1 commit
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BIT(), GENMASK(), etc. are useful to define register bits of hardware.
However, low-level code is often written in assembly, where they are
not available due to the hard-coded 1UL, 0UL.In fact, in-kernel headers such as arch/arm64/include/asm/sysreg.h
use _BITUL() instead of BIT() so that the register bit macros are
available in assembly.Using macros in include/uapi/linux/const.h have two reasons:
[1] For use in uapi headers
We should use underscore-prefixed variants for user-space.[2] For use in assembly code
Since _BITUL() uses UL(1) instead of 1UL, it can be used as an
alternative of BIT().For [2], it is pretty easy to change BIT() etc. for use in assembly.
This allows to replace _BUTUL() in kernel-space headers with BIT().
Link: http://lkml.kernel.org/r/20190609153941.17249-1-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada
Cc: Catalin Marinas
Cc: Christian Borntraeger
Cc: Heiko Carstens
Cc: Vasily Gorbik
Cc: Vineet Gupta
Cc: Will Deacon
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Jun, 2018
1 commit
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In preparation for implementing the asm-generic atomic bitops in terms
of atomic_long_*(), we need to prevent implementations from
pulling in . A common reason for this include is for the
BITS_PER_BYTE definition, so move this and some other BIT() and masking
macros into a new header file, .Signed-off-by: Will Deacon
Acked-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-arm-kernel@lists.infradead.org
Cc: yamada.masahiro@socionext.com
Link: https://lore.kernel.org/lkml/1529412794-17720-4-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar
