Messages in this thread Patch in this message | | | From | Sebastian Frias <> | Subject | [PATCH v2] add equivalent of BIT(x) for bitfields | Date | Mon, 5 Dec 2016 18:49:30 +0100 |
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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 <sf84@laposte.net> ---
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
--- include/linux/bitops.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index a83c822..641675d 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -24,6 +24,20 @@ #define GENMASK_ULL(h, l) \ (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) +#ifdef __KERNEL__ +/* + * Equivalent of BIT(x) but for contiguous bitfields + * GENVALUE(1, 0,0xff) = 0x00000003 + * GENVALUE(3, 0,0xff) = 0x0000000f + * GENVALUE(15,8,0xff) = 0x0000ff00 + * GENVALUE(6, 6, 1) = 0x00000040 == BIT(6) + */ +#define GENVALUE(msb, lsb, val) \ + (((val) << (lsb)) & (GENMASK((msb), (lsb)))) +#define GENVALUE_ULL(msb, lsb, val) \ + (((val) << (lsb)) & (GENMASK_ULL((msb), (lsb)))) +#endif + extern unsigned int __sw_hweight8(unsigned int w); extern unsigned int __sw_hweight16(unsigned int w); extern unsigned int __sw_hweight32(unsigned int w); -- 1.8.3.1
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