Messages in this thread Patch in this message | | | Subject | Re: [PATCH] bitops: move BITS() macro to the bitops file | From | Joe Perches <> | Date | Wed, 07 Aug 2013 03:33:34 -0700 |
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On Wed, 2013-08-07 at 11:06 +0200, Linus Walleij wrote: > This macro was invented by Mattias Nilsson for the usecase > where you want to set a sequence of bits inside a n-bit > word, while leaving the head and tail of the sequence all > zeroes. For example: > > #include <linux/bitops.h>
BITS is a name that's not easily reused because it's already in use in a few other places.
There are a few conflicts.
$ git grep -E "^\s*#\s*define\s+\bBITS\b" arch/arc/include/asm/disasm.h:#define BITS(word, s, e) (((word) >> (s)) & (~((-2) << ((e) - (s))))) drivers/input/keyboard/tnetv107x-keypad.c:#define BITS(x) (BIT(x) - 1) drivers/mfd/dbx500-prcmu-regs.h:#define BITS(_start, _end) ((BIT(_end) - BIT(_start)) + BIT(_end)) drivers/net/wireless/iwlwifi/mvm/fw-api-bt-coex.h:#define BITS(nb) (BIT(nb) - 1) fs/select.c:#define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) lib/zlib_inflate/inflate.c:#define BITS(n) \ sound/core/oss/rate.c:#define BITS (1<<SHIFT)
> u16 mask = BITS(4, 12); > > Yields a mask like this: > > 0001111111110000 [] > diff --git a/drivers/mfd/dbx500-prcmu-regs.h b/drivers/mfd/dbx500-prcmu-regs.h [] > @@ -13,8 +13,6 @@ [] > -#define BITS(_start, _end) ((BIT(_end) - BIT(_start)) + BIT(_end))
> diff --git a/include/linux/bitops.h b/include/linux/bitops.h [] > @@ -6,6 +6,7 @@ [] > +#define BITS(_start, _end) ((BIT(_end) - BIT(_start)) + BIT(_end))
Maybe use a statement expression to make sure the start and end accesses are done only once.
#define BITS(start, end) \ ({ \ unsigned long high = BIT(end); \ unsigned long low = BIT(start); \ unsigned long rtn = high + (high - low); \ rtn; \ })
I suggest | instead of + too.
Maybe add a WARN when low > high too. Maybe make it a function to consolidate any WARN instead of inline expansion.
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