On 07/12/16 12:05, Jakub Kicinski wrote: > On Wed, 7 Dec 2016 11:00:57 +0100, Sebastian Frias wrote: >> On 07/12/16 09:42, Kalle Valo wrote: >>> Sebastian Frias <s...@laposte.net> writes: >>> >>>> Introduce GENVALUE(msb, lsb, value) macro to ease dealing with >>>> continuous bitfields, just as BIT(x) does for single bits. >>>> >>>> GENVALUE_ULL(msb, lsb, value) macro is also added. >>>> >>>> This is useful mostly for creating values to be packed together >>>> via OR operations, ex: >>>> >>>> u32 val = 0x11110000; >>>> val |= GENVALUE(19, 12, 0x5a); >>>> >>>> now 'val = 0x1115a000' >>>> >>>> >>>> Signed-off-by: Sebastian Frias <s...@laposte.net> >>>> Link: https://marc.info/?l=linux-kernel&m=148094498711000&w=2 >>>> --- >>>> >>>> Change in v2: >>>> - rename the macro to GENVALUE as proposed by Linus >>>> - longer comment attempts to show use case for the macro as >>>> proposed by Borislav >>>> >>>> Change in v3: >>>> - use BUILD_BUG_ON_ZERO() to break if some input parameters >>>> (essentially 'lsb' but also 'msb') are not constants as >>>> proposed by Linus. >>>> Indeed, 'lsb' is used twice so it cannot have side-effects; >>>> 'msb' is subjected to same constraints for consistency. >>> >>> (I missed there was v3 already, but I'll repeat what I said in v1.) >>> >>> Please check FIELD_PREP() from include/linux/bitfield.h, doesn't it >>> already do the same? >> >> Indeed, it appears to do the same :-) >> Any reason why "include/linux/bitfield.h" is not included by default in >> bitops.h? > > Hi! > > The code is in a separate header because of circular dependencies > (coming from bug.h including bitops.h, IIRC). You could possibly add an > include of bitfield.h in bitops.h if you're very careful, I haven't > tried TBH :) >
Well, the following seems to work just fine: diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index f6505d8..24c7480 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -15,8 +15,6 @@ #ifndef _LINUX_BITFIELD_H #define _LINUX_BITFIELD_H -#include <linux/bug.h> - /* * Bitfield access macros * diff --git a/include/linux/bitops.h b/include/linux/bitops.h index a83c822..7e5fab8 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -24,6 +24,8 @@ #define GENMASK_ULL(h, l) \ (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) +#include "bitfield.h" + extern unsigned int __sw_hweight8(unsigned int w); extern unsigned int __sw_hweight16(unsigned int w); extern unsigned int __sw_hweight32(unsigned int w); Is there a way to be sure it works in all cases? Otherwise I could just submit that, right?