netdev - Re: [PATCH v2 3/7] lib/hexdump.c: Optionally suppress lines of repeated bytes

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Message-ID: <CAMuHMdVefYTgHzGKBc0ebku1z8V3wsM0ydN+6-S2nFKaB8eH_Q@mail.gmail.com>
Date:   Mon, 13 May 2019 09:01:14 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Alastair D'Silva" <alastair@....ibm.com>
Cc:     alastair@...ilva.org, Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Karsten Keil <isdn@...ux-pingi.de>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Laight <David.Laight@...lab.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, ath10k@...ts.infradead.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        scsi <linux-scsi@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        driverdevel <devel@...verdev.osuosl.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2 3/7] lib/hexdump.c: Optionally suppress lines of
 repeated bytes

Hi Alastair,

Thanks for your patch!

On Wed, May 8, 2019 at 9:04 AM Alastair D'Silva <alastair@....ibm.com> wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
>
> Some buffers may only be partially filled with useful data, while the rest
> is padded (typically with 0x00 or 0xff).
>
> This patch introduces a flag to allow the supression of lines of repeated
> bytes,

Given print_hex_dump() operates on entities of groupsize (1, 2, 4, or 8)
bytes, wouldn't it make more sense to consider repeated groups instead
of repeated bytes?

> which are replaced with '** Skipped %u bytes of value 0x%x **'

Using a custom message instead of just "*", like "hexdump" uses, will
require preprocessing the output when recovering the original binary
data by feeding it to e.g. "xxd".
This may sound worse than it is, though, as I never got "xxd" to work
without preprocessing anyway ;-)

    $ cat $(type -p unhexdump)
    #!/bin/sh
    sed 's/^[0-9a-f]*//' $1 | xxd -r -p | dd conv=swab

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds