linux-kernel - Re: [PATCH 0/4] log2: make is_power_of

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Message-ID: <7e7fa796-2614-92ea-012b-aa04f04a7312@amd.com>
Date:   Thu, 30 Mar 2023 12:59:18 +0200
From:   Christian König <christian.koenig@....com>
To:     Jani Nikula <jani.nikula@...el.com>, linux-kernel@...r.kernel.org
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Gow <davidgow@...gle.com>
Subject: Re: [PATCH 0/4] log2: make is_power_of_2() more generic

Am 30.03.23 um 12:42 schrieb Jani Nikula:
> is_power_of_2() only works for types <= sizeof(unsigned long) and it's
> also not a constant expression. There are a number of places in kernel
> where is_power_of_2() is called on u64, which fails on 32-bit
> builds. Try to remedy that. While at it, make it a constant expression
> when possible.
>
> I admit I've only lightly tested this, and I haven't tried it with
> allmodconfig.

Looks good to me from a one mile high level pov. But I'm really not an 
expert on that type of compiler magic, so only:

Acked-by: Christian König <christian.koenig@....com>

for the series.

Regards,
Christian.

>
>
> Jani Nikula (4):
>    log2: add helper __IS_POWER_OF_2()
>    log2: have is_power_of_2() support bigger types than unsigned long
>    log2: allow use of is_power_of_2() in constant expressions
>    drm/i915/reg: use is_power_of_2() from log2.h
>
>   drivers/gpu/drm/i915/i915_reg_defs.h |  7 +------
>   include/linux/log2.h                 | 25 ++++++++++++++++++++-----
>   2 files changed, 21 insertions(+), 11 deletions(-)
>