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Message-ID: <574d3a14-6b6e-3ad2-2ce3-48c9d76e205c@kernel.org>
Date:   Thu, 17 Aug 2023 22:34:39 +0200
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Subject: Re: [PATCH 2/4] linux/array_size.h: Add ARRAY_SIZE_OF_FIELD()
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To:     Lucas Segarra Fernandez <lucas.segarra.fernandez@intel.com>,
        herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org
Cc:     linux-crypto@vger.kernel.org, qat-linux@intel.com,
        andriy.shevchenko@intel.com,
        Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
References: <20230817143352.132583-1-lucas.segarra.fernandez@intel.com>
 <20230817143352.132583-3-lucas.segarra.fernandez@intel.com>
From:   Alejandro Colomar <alx@kernel.org>
Organization: Linux
In-Reply-To: <20230817143352.132583-3-lucas.segarra.fernandez@intel.com>
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From: Alejandro Colomar <alx@kernel.org>
To: Lucas Segarra Fernandez <lucas.segarra.fernandez@intel.com>,
 herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org
Cc: linux-crypto@vger.kernel.org, qat-linux@intel.com,
 andriy.shevchenko@intel.com, Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
 Andy Shevchenko <andy.shevchenko@gmail.com>
Message-ID: <574d3a14-6b6e-3ad2-2ce3-48c9d76e205c@kernel.org>
Subject: Re: [PATCH 2/4] linux/array_size.h: Add ARRAY_SIZE_OF_FIELD()
References: <20230817143352.132583-1-lucas.segarra.fernandez@intel.com>
 <20230817143352.132583-3-lucas.segarra.fernandez@intel.com>
In-Reply-To: <20230817143352.132583-3-lucas.segarra.fernandez@intel.com>

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Hi Lucas,

On 2023-08-17 16:33, Lucas Segarra Fernandez wrote:
> Introduce ARRAY_SIZE_OF_FIELD() in order to get the number of elements
> of an array struct field.
>=20
> Signed-off-by: Lucas Segarra Fernandez <lucas.segarra.fernandez@intel.c=
om>
> Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> ---
>  include/linux/array_size.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>=20
> diff --git a/include/linux/array_size.h b/include/linux/array_size.h
> index 06d7d83196ca..37dac0473b5c 100644
> --- a/include/linux/array_size.h
> +++ b/include/linux/array_size.h
> @@ -10,4 +10,12 @@
>   */
>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_ar=
ray(arr))
> =20
> +/*
> + * ARRAY_SIZE_OF_FIELD - get the number of elements of an array struct=
 field
> + *
> + * @TYPE: The structure containing the field of interest
> + * @MEMBER: The array field to be sized
> + */
> +#define ARRAY_SIZE_OF_FIELD(TYPE, MEMBER) ARRAY_SIZE((((TYPE *)0)->MEM=
BER))

Some comment about the name:

ARRAY_SIZE() is rather ambiguous, as there's array_size()[1], which means=
 the
number of bytes needed to represent the array.  I suggest a name based on=


-  _Lengthof()  It has been proposed to ISO C to get the number of elemen=
ts
                of an array:
                <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2529.p=
df>.

-  sizeof_field()  The kernel macro for the size of a struct member

So, how about lengthof_field()?


Cheers,
Alex


[1]:  The definition of array_size() is here:

$ grep -rnB10 define.array_size include/linux/overflow.h=20
238-/**
239- * array_size() - Calculate size of 2-dimensional array.
240- * @a: dimension one
241- * @b: dimension two
242- *
243- * Calculates size of 2-dimensional array: @a * @b.
244- *
245- * Returns: number of bytes needed to represent the array or SIZE_MAX=
 on
246- * overflow.
247- */
248:#define array_size(a, b)	size_mul(a, b)


> +
>  #endif  /* _LINUX_ARRAY_SIZE_H */

--=20
<http://www.alejandro-colomar.es/>
GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5

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