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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Alexander Potapenko <glider@google.com>
Cc: catalin.marinas@arm.com, will@kernel.org, pcc@google.com,
	andreyknvl@gmail.com, aleksander.lobakin@intel.com,
	linux@rasmusvillemoes.dk, yury.norov@gmail.com,
	alexandru.elisei@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, eugenis@google.com,
	syednwaris@gmail.com, william.gray@linaro.org,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v7 1/5] lib/bitmap: add bitmap_{read,write}()
Date: Wed, 11 Oct 2023 20:59:59 +0300	[thread overview]
Message-ID: <ZSbinxApgdd+aif2@smile.fi.intel.com> (raw)
In-Reply-To: <20231011172836.2579017-2-glider@google.com>

On Wed, Oct 11, 2023 at 07:28:31PM +0200, Alexander Potapenko wrote:
> From: Syed Nayyar Waris <syednwaris@gmail.com>
> 
> The two new functions allow reading/writing values of length up to
> BITS_PER_LONG bits at arbitrary position in the bitmap.
> 
> The code was taken from "bitops: Introduce the for_each_set_clump macro"
> by Syed Nayyar Waris with a number of changes and simplifications:
>  - instead of using roundup(), which adds an unnecessary dependency
>    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
>  - indentation is reduced by not using else-clauses (suggested by
>    checkpatch for bitmap_get_value());
>  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
>    and bitmap_write();
>  - some redundant computations are omitted.

I realized that the corner case with these functions is when agnostic user
wants to read / write > 32 bits at a time without ifdeffery applied.

At bare minimum this has to be documented explicitly, that callers
may have an issue of the above calls on 32-bit platforms.

-- 
With Best Regards,
Andy Shevchenko



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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Alexander Potapenko <glider@google.com>
Cc: catalin.marinas@arm.com, will@kernel.org, pcc@google.com,
	andreyknvl@gmail.com, aleksander.lobakin@intel.com,
	linux@rasmusvillemoes.dk, yury.norov@gmail.com,
	alexandru.elisei@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, eugenis@google.com,
	syednwaris@gmail.com, william.gray@linaro.org,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v7 1/5] lib/bitmap: add bitmap_{read,write}()
Date: Wed, 11 Oct 2023 20:59:59 +0300	[thread overview]
Message-ID: <ZSbinxApgdd+aif2@smile.fi.intel.com> (raw)
In-Reply-To: <20231011172836.2579017-2-glider@google.com>

On Wed, Oct 11, 2023 at 07:28:31PM +0200, Alexander Potapenko wrote:
> From: Syed Nayyar Waris <syednwaris@gmail.com>
> 
> The two new functions allow reading/writing values of length up to
> BITS_PER_LONG bits at arbitrary position in the bitmap.
> 
> The code was taken from "bitops: Introduce the for_each_set_clump macro"
> by Syed Nayyar Waris with a number of changes and simplifications:
>  - instead of using roundup(), which adds an unnecessary dependency
>    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
>  - indentation is reduced by not using else-clauses (suggested by
>    checkpatch for bitmap_get_value());
>  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
>    and bitmap_write();
>  - some redundant computations are omitted.

I realized that the corner case with these functions is when agnostic user
wants to read / write > 32 bits at a time without ifdeffery applied.

At bare minimum this has to be documented explicitly, that callers
may have an issue of the above calls on 32-bit platforms.

-- 
With Best Regards,
Andy Shevchenko



  reply	other threads:[~2023-10-11 18:00 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-11 17:28 [PATCH v7 0/5] Implement MTE tag compression for swapped pages Alexander Potapenko
2023-10-11 17:28 ` Alexander Potapenko
2023-10-11 17:28 ` [PATCH v7 1/5] lib/bitmap: add bitmap_{read,write}() Alexander Potapenko
2023-10-11 17:28   ` Alexander Potapenko
2023-10-11 17:59   ` Andy Shevchenko [this message]
2023-10-11 17:59     ` Andy Shevchenko
2023-10-12 12:55     ` Alexander Potapenko
2023-10-12 12:55       ` Alexander Potapenko
2023-10-11 17:28 ` [PATCH v7 2/5] lib/test_bitmap: add tests for bitmap_{read,write}() Alexander Potapenko
2023-10-11 17:28   ` Alexander Potapenko
2023-10-11 18:02   ` Andy Shevchenko
2023-10-11 18:02     ` Andy Shevchenko
2023-10-12 13:22     ` Alexander Potapenko
2023-10-12 13:22       ` Alexander Potapenko
2023-10-11 17:28 ` [PATCH v7 3/5] arm64: mte: implement CONFIG_ARM64_MTE_COMP Alexander Potapenko
2023-10-11 17:28   ` Alexander Potapenko
2023-10-11 17:28 ` [PATCH v7 4/5] arm64: mte: add a test for MTE tags compression Alexander Potapenko
2023-10-11 17:28   ` Alexander Potapenko
2023-10-11 17:28 ` [PATCH v7 5/5] arm64: mte: add compression support to mteswap.c Alexander Potapenko
2023-10-11 17:28   ` Alexander Potapenko

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