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Message-ID: <66a0c8210cf9e7dfcc3fa2d247de1eebd5a8acb7.camel@perches.com>
Subject: Re: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro
From:   Joe Perches <joe@perches.com>
To:     Keith Busch <kbusch@kernel.org>, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-crypto@vger.kernel.org,
        x86@kernel.org, linux-kernel@vger.kernel.org
Cc:     axboe@kernel.dk, hch@lst.de, martin.petersen@oracle.com,
        colyli@suse.de, Bart Van Assche <bvanassche@acm.org>
Date:   Tue, 22 Feb 2022 08:45:53 -0800
In-Reply-To: <20220222163144.1782447-5-kbusch@kernel.org>
References: <20220222163144.1782447-1-kbusch@kernel.org>
         <20220222163144.1782447-5-kbusch@kernel.org>
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On Tue, 2022-02-22 at 08:31 -0800, Keith Busch wrote:
> Recent data integrity field enhancements allow 48-bit reference tags.
> Introduce a helper macro since this will be a repeated operation.
[]
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
[]
> @@ -63,6 +63,12 @@
>  }					\
>  )
>  
> +/**
> + * lower_48_bits - return bits 0-47 of a number
> + * @n: the number we're accessing
> + */
> +#define lower_48_bits(n) ((u64)((n) & 0xffffffffffffull))

why not make this a static inline function?
And visually, it's difficult to quickly count a repeated character to 12.

Perhaps:

static inline u64 lower_48_bits(u64 val)
{
	return val & GENMASK_ULL(47, 0);
}