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Re: [PATCH v4 07/11] xen/arm: bitops: Implement a ffsll function
- To: Julien Grall <julien@xxxxxxx>
- From: Rahul Singh <Rahul.Singh@xxxxxxx>
- Date: Mon, 18 Jan 2021 15:32:50 +0000
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- Thread-topic: [PATCH v4 07/11] xen/arm: bitops: Implement a ffsll function
Hello Julien,
> On 15 Jan 2021, at 12:16 pm, Julien Grall <julien@xxxxxxx> wrote:
>
> Hi Rahul,
>
> On 08/01/2021 14:46, Rahul Singh wrote:
>> Implement the ffsll based on built-in function "__builtin_ffsll()"
>> ffsll will return one plus the index of the least significant 1-bit in
>> doublewords or if doublewords is zero, returns zero.
>> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
>> ---
>> Changes in V4:
>> - This patch is introduce in this verison.
>> ---
>> xen/include/asm-arm/bitops.h | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>> diff --git a/xen/include/asm-arm/bitops.h b/xen/include/asm-arm/bitops.h
>> index 71ae14cab3..7f83ee1828 100644
>> --- a/xen/include/asm-arm/bitops.h
>> +++ b/xen/include/asm-arm/bitops.h
>> @@ -170,6 +170,18 @@ static inline unsigned int find_first_set_bit(unsigned
>> long word)
>> return ffsl(word) - 1;
>> }
>> +/**
>> + * ffsll - find the first least significant set bit
>> + * @doubleword: double word to search
>> + *
>> + * Returns one plus the index of the least significant 1-bit in @doubleword
>> + * or if doubleword is zero, returns zero.
>> + */
>> +static inline int ffsll(long long doubleword)
>
> If I am not mistaken, we already have an helper doing exactly the same (see
> ffs64() in xen/bitops.h).
>
> Can you check if it is effectively the case and use it?
I checked we can use the ffs64() for SMMUv3 driver as it is doing exactly the
same as ffsll().
I will modify the code to use the ffs64() in place of ffsll().
Regards,
Rahul
>
> Cheers,
>
> --
> Julien Grall
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