linux-kernel - RE: [PATCH v2 3/7] lib/hexdump.c: Optionally suppress lines of repeated bytes

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Message-ID: <04de01d5095e$7f6af730$7e40e590$@d-silva.org>
Date:   Mon, 13 May 2019 17:35:47 +1000
From:   "Alastair D'Silva" <alastair@...ilva.org>
To:     "'Geert Uytterhoeven'" <geert@...ux-m68k.org>,
        "'Alastair D'Silva'" <alastair@....ibm.com>
Cc:     "'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>,
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        "'Linux FS Devel'" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH v2 3/7] lib/hexdump.c: Optionally suppress lines of repeated bytes

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: Monday, 13 May 2019 5:01 PM
> 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!

And thanks for your politeness :)

> 
> 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?

Maybe, it would mean that subsequent addresses may not be a multiple of rowsize though, which is useful.

> > 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 ;-)

I think showing the details of the skipped values is useful when reading the output directly. In situations where binary extracts are desired, the feature can always be disabled.

-- 
Alastair D'Silva           mob: 0423 762 819
skype: alastair_dsilva     msn: alastair@...ilva.org
blog: http://alastair.d-silva.org    Twitter: @EvilDeece