From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matan Azrad <matan@mellanox.com>
Subject: Re: [PATCH 1/2] eal: add API to align integer to
	previous	power of 2
Date: Sun, 18 Feb 2018 06:11:20 +0000
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To: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>,
 "jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>, "Thomas
 Monjalon" <thomas@monjalon.net>
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Hi Pavan

Please see some comments below.

 From: Pavan Nikhilesh, Saturday, February 17, 2018 12:50 PM
> Add 32b and 64b API's to align the given integer to the previous power of=
 2.
>=20
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> ---
>  lib/librte_eal/common/include/rte_common.h | 36
> ++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>=20
> diff --git a/lib/librte_eal/common/include/rte_common.h
> b/lib/librte_eal/common/include/rte_common.h
> index c7803e41c..126914f07 100644
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -259,6 +259,24 @@ rte_align32pow2(uint32_t x)
>  	return x + 1;
>  }
>=20
> +/**
> + * Aligns input parameter to the previous power of 2
> + *
> + * @param x
> + *   The integer value to algin
> + *
> + * @return
> + *   Input parameter aligned to the previous power of 2

I think the zero case(x=3D0) result should be documented.

> + */
> +static inline uint32_t
> +rte_align32lowpow2(uint32_t x)

What do you think about " rte_align32prevpow2"?

> +{
> +	x =3D rte_align32pow2(x);

	In case of  x is power of 2 number(already aligned), looks like the result=
 here is x and the final result is (x >> 1)?
	Is it as you expect?

> +	x--;
> +
> +	return x - (x >> 1);

Why can't the implementation just be:
return  rte_align32pow2(x) >> 1;

If the above is correct, Are you sure we need this API?

> +}
> +
>  /**
>   * Aligns 64b input parameter to the next power of 2
>   *
> @@ -282,6 +300,24 @@ rte_align64pow2(uint64_t v)
>  	return v + 1;
>  }
>=20
> +/**
> + * Aligns 64b input parameter to the previous power of 2
> + *
> + * @param v
> + *   The 64b value to align
> + *
> + * @return
> + *   Input parameter aligned to the previous power of 2
> + */
> +static inline uint64_t
> +rte_align64lowpow2(uint64_t v)
> +{
> +	v =3D rte_align64pow2(v);
> +	v--;
> +
> +	return v - (v >> 1);
> +}
> +

Same comments for 64b API.

>  /*********** Macros for calculating min and max **********/
>=20
>  /**
> --
> 2.16.1


If it is a new API, I think it should be added to the map file and to be ta=
gged as experimental. No?

Matan