linux-kernel - Re: [PATCH v2 2/2] hexdump: Allow skipping identical lines

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Message-ID: <87wmepvnns.fsf@bootlin.com>
Date: Mon, 20 Jan 2025 10:29:27 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: David Laight <david.laight.linux@...il.com>
Cc: Petr Mladek <pmladek@...e.com>,  Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>,  Steven Rostedt
 <rostedt@...dmis.org>,  Rasmus Villemoes <linux@...musvillemoes.dk>,
  Sergey Senozhatsky <senozhatsky@...omium.org>,  Jonathan Corbet
 <corbet@....net>,  John Ogness <john.ogness@...utronix.de>,  Andrew Morton
 <akpm@...ux-foundation.org>,  Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>,  linux-doc@...r.kernel.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] hexdump: Allow skipping identical lines

Hello David & Petr,

On 17/01/2025 at 19:25:22 GMT, David Laight <david.laight.linux@...il.com> wrote:

> On Fri, 17 Jan 2025 17:27:26 +0100
> Petr Mladek <pmladek@...e.com> wrote:
>
> ...
>> IMHO, it is perfectly fine to add support for skipping identical lines
>> only to print_hex_dump(). And I would go even further and replace
>> 
>> void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
>> 		    int rowsize, int groupsize,
>> 		    const void *buf, size_t len, bool ascii)
>> 
>> with
>> 
>> void print_hex_dump(const char *level, const char *prefix_str,
>> 		    enum hex_dump_type,
>> 		    int rowsize, int groupsize,
>> 		    const void *buf, size_t len)
>> 
>> and combine all the flags into the one enum:
>> 
>> enum hex_dump_type {
>> 	DUMP_HEX_ONLY = 0,
>> 	DUMP_HEX_AND_ASCII = BIT(1),
>> 	DUMP_PREFIX_ADDRESS = BIT(2),
>> 	DUMP_PREFIX_OFFSET = BIT(3),
>> 	DUMP_SKIP_IDENTICAL_LINES = BIT(4),
>> };

Would a single enum (in the prototype of the function) work? I like the
idea but we need some kind of OR combination to be supported, typically:

DUMP_HEX_AND_ASCII | DUMP_PREFIX_OFFSET | DUMP_SKIP_IDENTICAL_LINES

Maybe something like:

void print_hex(const char *level, const char *prefix_str,
	       int rowsize, int groupsize,
	       const void *buf, size_t len,
               unsigned int dump_flags) // flags instead of enum?

enum hex_dump_flags {
        // I'm not sure what to do with the default value?
	DUMP_ASCII = BIT(0), // renamed?
	DUMP_PREFIX_ADDRESS = BIT(1),
	DUMP_PREFIX_OFFSET = BIT(2),
	DUMP_SKIP_IDENTICAL_LINES = BIT(3),
};

>> How does that sound, please?
>
> Rename it as (say) print_hex() and add wrappers for the existing callers?

That would avoid the treewide changes, so yes I can try that, definitely.

Thanks,
Miquèl