Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   "Alastair D'Silva" <alastair@d-silva.org>
To:     "'David Laight'" <David.Laight@ACULAB.COM>,
        "'Alastair D'Silva'" <alastair@au1.ibm.com>
Cc:     "'Jani Nikula'" <jani.nikula@linux.intel.com>,
        "'Joonas Lahtinen'" <joonas.lahtinen@linux.intel.com>,
        "'Rodrigo Vivi'" <rodrigo.vivi@intel.com>,
        "'David Airlie'" <airlied@linux.ie>,
        "'Daniel Vetter'" <daniel@ffwll.ch>,
        "'Dan Carpenter'" <dan.carpenter@oracle.com>,
        "'Karsten Keil'" <isdn@linux-pingi.de>,
        "'Jassi Brar'" <jassisinghbrar@gmail.com>,
        "'Tom Lendacky'" <thomas.lendacky@amd.com>,
        "'David S. Miller'" <davem@davemloft.net>,
        "'Jose Abreu'" <Jose.Abreu@synopsys.com>,
        "'Kalle Valo'" <kvalo@codeaurora.org>,
        "'Stanislaw Gruszka'" <sgruszka@redhat.com>,
        "'Benson Leung'" <bleung@chromium.org>,
        "'Enric Balletbo i Serra'" <enric.balletbo@collabora.com>,
        "'James E.J. Bottomley'" <jejb@linux.ibm.com>,
        "'Martin K. Petersen'" <martin.petersen@oracle.com>,
        "'Greg Kroah-Hartman'" <gregkh@linuxfoundation.org>,
        "'Alexander Viro'" <viro@zeniv.linux.org.uk>,
        "'Petr Mladek'" <pmladek@suse.com>,
        "'Sergey Senozhatsky'" <sergey.senozhatsky@gmail.com>,
        "'Steven Rostedt'" <rostedt@goodmis.org>,
        "'Andrew Morton'" <akpm@linux-foundation.org>,
        <intel-gfx@lists.freedesktop.org>,
        <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        <netdev@vger.kernel.org>, <ath10k@lists.infradead.org>,
        <linux-wireless@vger.kernel.org>, <linux-scsi@vger.kernel.org>,
        <linux-fbdev@vger.kernel.org>, <devel@driverdev.osuosl.org>,
        <linux-fsdevel@vger.kernel.org>
References: <20190508070148.23130-1-alastair@au1.ibm.com> <20190508070148.23130-5-alastair@au1.ibm.com> <c98a499a4e824bcd824d5ad53d037c67@AcuMS.aculab.com>
In-Reply-To: <c98a499a4e824bcd824d5ad53d037c67@AcuMS.aculab.com>
Subject: RE: [PATCH v2 4/7] lib/hexdump.c: Replace ascii bool in hex_dump_to_buffer with flags
Date:   Wed, 8 May 2019 21:41:15 +1000
Message-ID: <0a1c01d50592$f90f6f00$eb2e4d00$@d-silva.org>
MIME-Version: 1.0
Content-Type: text/plain;
        charset="utf-8"
Content-Transfer-Encoding: quoted-printable
Thread-Index: AQGz7QD7bMLLz3XdMyQiMIIzLY+D4AHts+RHAcfZVGymhZij0A==
Content-Language: en-au
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> -----Original Message-----
> From: David Laight <David.Laight@ACULAB.COM>
> Sent: Wednesday, 8 May 2019 7:20 PM
> To: 'Alastair D'Silva' <alastair@au1.ibm.com>; alastair@d-silva.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>; Joonas Lahtinen
> <joonas.lahtinen@linux.intel.com>; Rodrigo Vivi =
<rodrigo.vivi@intel.com>;
> David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Dan
> Carpenter <dan.carpenter@oracle.com>; Karsten Keil <isdn@linux-
> pingi.de>; Jassi Brar <jassisinghbrar@gmail.com>; Tom Lendacky
> <thomas.lendacky@amd.com>; David S. Miller <davem@davemloft.net>;
> Jose Abreu <Jose.Abreu@synopsys.com>; Kalle Valo
> <kvalo@codeaurora.org>; Stanislaw Gruszka <sgruszka@redhat.com>;
> Benson Leung <bleung@chromium.org>; Enric Balletbo i Serra
> <enric.balletbo@collabora.com>; James E.J. Bottomley
> <jejb@linux.ibm.com>; Martin K. Petersen <martin.petersen@oracle.com>;
> Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Alexander Viro
> <viro@zeniv.linux.org.uk>; Petr Mladek <pmladek@suse.com>; Sergey
> Senozhatsky <sergey.senozhatsky@gmail.com>; Steven Rostedt
> <rostedt@goodmis.org>; Andrew Morton <akpm@linux-foundation.org>;
> intel-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; =
linux-
> kernel@vger.kernel.org; netdev@vger.kernel.org;
> ath10k@lists.infradead.org; linux-wireless@vger.kernel.org; linux-
> scsi@vger.kernel.org; linux-fbdev@vger.kernel.org;
> devel@driverdev.osuosl.org; linux-fsdevel@vger.kernel.org
> Subject: RE: [PATCH v2 4/7] lib/hexdump.c: Replace ascii bool in
> hex_dump_to_buffer with flags
>=20
> From: Alastair D'Silva
> > Sent: 08 May 2019 08:02
> > To: alastair@d-silva.org
> ...
> > --- a/include/linux/printk.h
> > +++ b/include/linux/printk.h
> > @@ -480,13 +480,13 @@ enum {
> >  	DUMP_PREFIX_OFFSET
> >  };
> >
> > -extern int hex_dump_to_buffer(const void *buf, size_t len, int =
rowsize,
> > -			      int groupsize, char *linebuf, size_t linebuflen,
> > -			      bool ascii);
> > -
> >  #define HEXDUMP_ASCII			(1 << 0)
> >  #define HEXDUMP_SUPPRESS_REPEATED	(1 << 1)
>=20
> These ought to be BIT(0) and BIT(1)

Thanks, I'll address that.

>=20
> > +extern int hex_dump_to_buffer(const void *buf, size_t len, int =
rowsize,
> > +			      int groupsize, char *linebuf, size_t linebuflen,
> > +			      u64 flags);
>=20
> Why 'u64 flags' ?
> How many flags do you envisage ??
> Your HEXDUMP_ASCII (etc) flags are currently signed values and might =
get
> sign extended causing grief.
> 'unsigned int flags' is probably sufficient.

I was trying to avoid having to change the prototype again in the =
future, but it's not a big deal, if enough work goes in to require more =
than 32 bits, it can be updated at that point.

>=20
> I've not really looked at the code, it seems OTT in places though.

I'll wait for more concrete criticisms here, this it a bit too vague to =
take any action on.

> If someone copies it somewhere where the performance matters (I've =
user
> space code which is dominated by its tracing!) then you don't want all =
the
> function calls and conditionals even if you want some of the =
functionality.

Calling hexdump (even in it's unaltered form) in performance critical =
code is always going to suck. As you mentioned before, it's all based =
around printf. A performance conscious user would be better off building =
their code around hex_asc_hi/lo instead (see lib/vsprintf.c:hex_string).

--=20
Alastair D'Silva           mob: 0423 762 819
skype: alastair_dsilva     msn: alastair@d-silva.org
blog: http://alastair.d-silva.org    Twitter: @EvilDeece