Re: [PATCH v5] xen: simplify bitmap_to_xenctl_bitmap for little endian

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/04/2025 10:30 am, Jan Beulich wrote:
> On 02.04.2025 11:21, Andrew Cooper wrote:
>> On 01/04/2025 11:09 am, Jan Beulich wrote:
>>> --- a/xen/common/bitmap.c
>>> +++ b/xen/common/bitmap.c
>>> @@ -359,12 +343,11 @@ static void bitmap_byte_to_long(unsigned
>>>  
>>>  #elif defined(__LITTLE_ENDIAN)
>>>  
>>> -static void bitmap_long_to_byte(uint8_t *bp, const unsigned long *lp,
>>> -                           unsigned int nbits)
>>> -{
>>> -   memcpy(bp, lp, DIV_ROUND_UP(nbits, BITS_PER_BYTE));
>>> -   clamp_last_byte(bp, nbits);
>>> -}
>>> +#define LITTLE_ENDIAN 1 /* For IS_ENABLED(). */
>> I guess I can fix this in my bswap series by giving __LITTLE_ENDIAN the
>> value of 1 when it is defined ?
> Hmm, that's an option, yes. Yet then I didn't pay close enough attention
> to that part of the respective patch in that series, as I was blindly
> assuming it to instead be
>
> #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> # define __LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__
> #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> # define __BIG_ENDIAN __ORDER_BIG_ENDIAN__
> #endif
>
> to keep the values of the symbols unaltered.

I saw no value doing that, after auditing that it was only ever used in
an #ifdef kind of way.  IS_ENABLED() is an extension of the same
concept, but requiring a 1 to work.

~Andrew