Messages in this thread | | | Subject | Re: [PATCH v2 08/30] Add sparc-specific parity functions | From | Zeng Zhaoxiu <> | Date | Thu, 7 Apr 2016 11:56:08 +0800 |
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在 2016年04月07日 02:44, Sam Ravnborg 写道: > Hi Zeng. > >> Use runtime patching for sparc64, lifted from hweight > No errors found in patch - but a few comments. > In general patch looks good.
Thanks. Sparc, powerpc, and x86 are all new to me.
>> +++ b/arch/sparc/include/asm/bitops_64.h >> @@ -47,6 +47,24 @@ unsigned int __arch_hweight16(unsigned int w); >> unsigned int __arch_hweight8(unsigned int w); >> >> #include <asm-generic/bitops/const_hweight.h> >> + >> +/* >> + * parityN: returns the parity of a N-bit word, >> + * i.e. the number of 1-bits in w modulo 2. >> + */ >> + >> +static inline unsigned int __arch_parity4(unsigned int w) >> +{ >> + w &= 0xf; >> + return (0x6996 >> w) & 1; >> +} > As Josef already said - this constant should have a name. > PARITY_BIT > ? >
Maybe PARITY_MAGIC?
>> +++ b/arch/sparc/kernel/sparc_ksyms_64.c >> @@ -45,6 +45,12 @@ EXPORT_SYMBOL(__arch_hweight16); >> EXPORT_SYMBOL(__arch_hweight32); >> EXPORT_SYMBOL(__arch_hweight64); >> >> +/* from parity.S */ >> +EXPORT_SYMBOL(__arch_parity8); >> +EXPORT_SYMBOL(__arch_parity16); >> +EXPORT_SYMBOL(__arch_parity32); >> +EXPORT_SYMBOL(__arch_parity64); > Did you compile this? > I wonder if bitops_64.h is indirectly included.
Yes.
>> index 0000000..b1945e3 >> --- /dev/null >> +++ b/arch/sparc/lib/parity.S >> @@ -0,0 +1,93 @@ >> +#include <linux/linkage.h> >> + >> + .text >> + .align 32 >> + >> +ENTRY(__arch_parity8) >> + srl %o0, 4, %g1 >> + xor %o0, %g1, %o0 >> + and %o0, 0xf, %o0 >> + sethi %hi(0x6996), %g1 >> + or %g1, %lo(0x6996), %g1 >> + srl %g1, %o0, %o0 >> + retl >> + and %o0, 1, %o0 >> +ENDPROC(__arch_parity8) > I know the level of comments in hweight is equal to none. > But please do not follow this bad example. > At least for each function a one-liner of the C code. > And in the top of the file maybe two lines that the functions > are patched at run-time if the processor has popc available. > > > Sam
OK. I will try, but my english is very poor! :-)
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