Re: [PATCH 1/6] bitops.h: add deposit16 function

[Miles Glenn]

Reviewed-by: Glenn Miles <milesg@linux.ibm.com>

On Thu, 2024-11-07 at 19:54 +0000, Titus Rwantare wrote:
> Makes it more explicit that 16 bit values are being used
> 
> Signed-off-by: Titus Rwantare <titusr@google.com>
> ---
>  include/qemu/bitops.h | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
> index 2c0a2fe751..05179e3ded 100644
> --- a/include/qemu/bitops.h
> +++ b/include/qemu/bitops.h
> @@ -459,6 +459,32 @@ static inline int64_t sextract64(uint64_t value,
> int start, int length)
>      return ((int64_t)(value << (64 - length - start))) >> (64 -
> length);
>  }
> 
> +/**
> + * deposit16:
> + * @value: initial value to insert bit field into
> + * @start: the lowest bit in the bit field (numbered from 0)
> + * @length: the length of the bit field
> + * @fieldval: the value to insert into the bit field
> + *
> + * Deposit @fieldval into the 16 bit @value at the bit field
> specified
> + * by the @start and @length parameters, and return the modified
> + * @value. Bits of @value outside the bit field are not modified.
> + * Bits of @fieldval above the least significant @length bits are
> + * ignored. The bit field must lie entirely within the 16 bit word.
> + * It is valid to request that all 16 bits are modified (ie @length
> + * 16 and @start 0).
> + *
> + * Returns: the modified @value.
> + */
> +static inline uint16_t deposit16(uint16_t value, int start, int
> length,
> +                                 uint16_t fieldval)
> +{
> +    uint16_t mask;
> +    assert(start >= 0 && length > 0 && length <= 16 - start);
> +    mask = (~0U >> (16 - length)) << start;
> +    return (value & ~mask) | ((fieldval << start) & mask);
> +}
> +
>  /**
>   * deposit32:
>   * @value: initial value to insert bit field into