linux-kernel - RE: [PATCH 3/4] lib/hexdump.c: Replace ascii bool in hex_dump_to

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Date:   Mon, 15 Apr 2019 20:44:39 +1000
From:   "Alastair D'Silva" <alastair@...ilva.org>
To:     "'David Laight'" <David.Laight@...LAB.COM>,
        "'Petr Mladek'" <pmladek@...e.com>
Cc:     "'Alastair D'Silva'" <alastair@....ibm.com>,
        "'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>,
        "'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>,
        "'Sergey Senozhatsky'" <sergey.senozhatsky@...il.com>,
        "'Steven Rostedt'" <rostedt@...dmis.org>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>,
        <intel-gfx@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <ath10k@...ts.infradead.org>,
        <linux-wireless@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <linux-fbdev@...r.kernel.org>, <devel@...verdev.osuosl.org>,
        <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH 3/4] lib/hexdump.c: Replace ascii bool in hex_dump_to_buffer with flags

> -----Original Message-----
> From: David Laight <David.Laight@...LAB.COM>
> Sent: Monday, 15 April 2019 8:21 PM
> To: 'Alastair D'Silva' <alastair@...ilva.org>; 'Petr Mladek'
> <pmladek@...e.com>
> Cc: 'Alastair D'Silva' <alastair@....ibm.com>; '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>; '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>; 'Sergey Senozhatsky'
> <sergey.senozhatsky@...il.com>; 'Steven Rostedt'
> <rostedt@...dmis.org>; 'Andrew Morton' <akpm@...ux-foundation.org>;
> intel-gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; linux-
> kernel@...r.kernel.org; netdev@...r.kernel.org;
> ath10k@...ts.infradead.org; linux-wireless@...r.kernel.org; linux-
> scsi@...r.kernel.org; linux-fbdev@...r.kernel.org;
> devel@...verdev.osuosl.org; linux-fsdevel@...r.kernel.org
> Subject: RE: [PATCH 3/4] lib/hexdump.c: Replace ascii bool in
> hex_dump_to_buffer with flags
> 
> From: Alastair D'Silva
> > Sent: 15 April 2019 11:07
> ...
> > In the above example the author only wants the hex output, while in
> > other situations, both hex & ASCII output is desirable. If you just
> > want ASCII output, the caller should just use a printk or one of it's
> wrappers.
> 
> Hexdump will 'sanitise' the ASCII.
> 

This is functionality that doesn't exist in the current hexdump implementation (you always get the hex version).

I think a better option would be to factor out the sanitisation and expose that as a separate function.

> Although I think you'd want a 'no hex' flag to suppress the hex.
> 
> Probably more useful flags are ones to suppress the address column.

This is already supported by the prefix_type parameter - are you proposing that we eliminate the parameter & combine it with flags?

> I've also used flags to enable (or disable) suppression of multiple lines of
> zeros of constant bytes.
> In that case you may want hexdump to return the flags for the next call when
> a large buffer is being dumped in fragments.
 
I'm afraid I don't quite follow here, hex_dump_to_buffer doesn't alter the flags, so the caller already knows it. 

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