linux-kernel - Re: [PATCH v4 5/7] lib/hexdump.c: Allow multiple groups to be separated by lines '|'

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Message-ID: <ef3aac0cb37fd7bb421db313e839809fd7649d05.camel@d-silva.org>
Date:   Wed, 26 Jun 2019 11:28:01 +1000
From:   "Alastair D'Silva" <alastair@...ilva.org>
To:     Joe Perches <joe@...ches.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-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 v4 5/7] lib/hexdump.c: Allow multiple groups to be
 separated by lines '|'

On Mon, 2019-06-24 at 22:37 -0700, Joe Perches wrote:
> On Tue, 2019-06-25 at 13:17 +1000, Alastair D'Silva wrote:
> > From: Alastair D'Silva <alastair@...ilva.org>
> > 
> > With the wider display format, it can become hard to identify how
> > many
> > bytes into the line you are looking at.
> > 
> > The patch adds new flags to hex_dump_to_buffer() and
> > print_hex_dump() to
> > print vertical lines to separate every N groups of bytes.
> > 
> > eg.
> > buf:00000000: 454d414e 43415053|4e495f45
> > 00584544  NAMESPAC|E_INDEX.
> > buf:00000010: 00000000 00000002|00000000
> > 00000000  ........|........
> > 
> > Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> > ---
> >  include/linux/printk.h |  3 +++
> >  lib/hexdump.c          | 59 ++++++++++++++++++++++++++++++++++++
> > ------
> >  2 files changed, 54 insertions(+), 8 deletions(-)
> > 
> > diff --git a/include/linux/printk.h b/include/linux/printk.h
> []
> > @@ -485,6 +485,9 @@ enum {
> >  
> >  #define HEXDUMP_ASCII			BIT(0)
> >  #define HEXDUMP_SUPPRESS_REPEATED	BIT(1)
> > +#define HEXDUMP_2_GRP_LINES		BIT(2)
> > +#define HEXDUMP_4_GRP_LINES		BIT(3)
> > +#define HEXDUMP_8_GRP_LINES		BIT(4)
> 
> These aren't really bits as only one value should be set
> as 8 overrides 4 and 4 overrides 2.

This should be the other way around, as we should be emitting alternate
seperators based on the smallest grouping (2 implies 4 and 8, and 4
implies 8). I'll fix the logic.

I can't come up with a better way to represent these without making the
API more complex, if you have a suggestion, I'm happy to hear it.

> 
> I would also expect this to be a value of 2 in your above
> example, rather than 8.  It's described as groups not bytes.
> 
> The example is showing a what would normally be a space ' '
> separator as a vertical bar '|' every 2nd grouping.
> 

The above example shows a group size of 4 bytes, and
HEXDUMP_2_GRP_LINES set, with 2 groups being 8 bytes.

I'll make that clearer in the commit message.

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