linux-kernel - Re: [PATCHv3 04/10] linux/kernel: introduce lower_48

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Date:   Tue, 22 Feb 2022 08:45:53 -0800
From:   Joe Perches <joe@...ches.com>
To:     Keith Busch <kbusch@...nel.org>, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-crypto@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     axboe@...nel.dk, hch@....de, martin.petersen@...cle.com,
        colyli@...e.de, Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro

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);
}