linux-kernel - Re: [PATCH v2 1/1] lib: Optimise hex_dump_to

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Message-ID: <Z86rSd88eSiJxV-M@smile.fi.intel.com>
Date: Mon, 10 Mar 2025 11:05:13 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: David Laight <david.laight.linux@...il.com>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christophe Leroy <christophe.leroy@....fr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>, nnac123@...ux.ibm.com,
	horms@...nel.org
Subject: Re: [PATCH v2 1/1] lib: Optimise hex_dump_to_buffer()

On Sat, Mar 08, 2025 at 09:34:21AM +0000, David Laight wrote:
> Fastpath the normal case of single byte output that fits in the buffer.
> Output byte groups (byteswapped on little-endian) without calling snprintf().
> Remove the restriction that rowsize must be 16 or 32.
> (All callers currently pass 16 or 32.)
> Remove the restriction that groupsize must be 8 or less.
> If groupsize isn't a power of 2 or doesn't divide into both len and
>   rowsize it is set to 1 (otherwise byteswapping is hard).
> Change the types of the rowsize and groupsize parameters to be unsigned types.
> 
> Fix the return value (should be zero) when both len and linebuflen are zero.
> 
> All the updated tests in lib/test_hexdump.c pass.
> Code size (x86-64) approximately halved.

...

> -extern int hex_dump_to_buffer(const void *buf, size_t len, int rowsize,
> -			      int groupsize, char *linebuf, size_t linebuflen,
> -			      bool ascii);
> +extern size_t hex_dump_to_buffer(const void *buf, size_t len, size_t rowsize,

Why is extern still here?

> +				 size_t groupsize, char *linebuf,
> +				 size_t linebuflen, bool ascii);

int - > size_t in the returned value is incorrect change.
This is explained in the comments to the test cases patch series.

-- 
With Best Regards,
Andy Shevchenko