[PATCH 1/2] include: sbi_bitmap: add bitmap_empty() function

[Anup Patel]

On Wed, Mar 11, 2026 at 6:21 PM Yu-Chien Peter Lin <peter.lin at sifive.com> wrote:
>
> Add bitmap_empty() to check if bitmap has no bits set.
>
> Unlike bitmap_weight() which calls sbi_popcount() on every word,
> bitmap_empty() uses simple non-zero comparisons with early exit.
>
> Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  include/sbi/sbi_bitmap.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/include/sbi/sbi_bitmap.h b/include/sbi/sbi_bitmap.h
> index 596bcc7d..80d3fe3b 100644
> --- a/include/sbi/sbi_bitmap.h
> +++ b/include/sbi/sbi_bitmap.h
> @@ -143,4 +143,20 @@ static inline int bitmap_weight(const unsigned long *src, int nbits)
>         return res;
>  }
>
> +static inline bool bitmap_empty(const unsigned long *src, int nbits)
> +{
> +       if (nbits == 0)
> +               return true;
> +
> +       if (small_const_nbits(nbits))
> +               return !(*src & BITMAP_LAST_WORD_MASK(nbits));
> +       else {
> +               size_t i, len = BITS_TO_LONGS(nbits);
> +               for (i = 0; i < len - 1; i++)
> +                       if (src[i])
> +                               return false;
> +               return !(src[len - 1] & BITMAP_LAST_WORD_MASK(nbits));
> +       }
> +}
> +
>  #endif
> --
> 2.53.0
>
>
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