Re: [PATCH 2/3] x86/hash: swap parameters of crc32_u32()

[Jan Beulich]

>>> On 22.02.14 at 13:09, Daniel Borkmann <dborkman@xxxxxxxxxx> wrote:
> On 02/21/2014 11:33 AM, Jan Beulich wrote:
>> ... to match its two callers (i.e. the alternative would have been to
>> swap the arguments at the call sites).
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Cc: Francesco Fusco <ffusco@xxxxxxxxxx>
>> Cc: Daniel Borkmann <dborkman@xxxxxxxxxx>
>> Cc: Thomas Graf <tgraf@xxxxxxxxxx>
>> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
>> ---
>>   arch/x86/lib/hash.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- 3.14-rc3-x86-hash-crc32.orig/arch/x86/lib/hash.c
>> +++ 3.14-rc3-x86-hash-crc32/arch/x86/lib/hash.c
>> @@ -37,7 +37,7 @@
>>   #include <asm/cpufeature.h>
>>   #include <asm/hash.h>
>>
>> -static inline u32 crc32_u32(u32 crc, u32 val)
>> +static inline u32 crc32_u32(u32 val, u32 crc)
>>   {
>>   #ifdef CONFIG_AS_CRC32
>>   	asm ("crc32l %1,%0\n" : "+r" (crc) : "rm" (val));
> 
> Can you elaborate?
> 
> Sorry, I need to ask here (even if it's a stupid question ;)) if this
> change is safe to do; are referring to a cleanup or fixing a concrete
> bug? The code is a modified version of the DPDK hash which you can find
> in [1]. Arguments of the caller are in the correct order, afaik.
> 
>    [1] http://dpdk.org/browse/dpdk/tree/lib/librte_hash/rte_hash_crc.h 

Yes, that file appears to be correct:

rte_hash_crc_4byte(uint32_t data, uint32_t init_val)

as opposed to 

static inline u32 crc32_u32(u32 crc, u32 val)

(quite obviously data <-> val and crc <-> init_val, supported
by the second argument in each caller being named "seed").

Jan

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