linux-kernel - Re: [PATCH v3 2/4] lib/hexdump.c: factor out generic hexdump formatting for reuse.

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Date:   Wed, 27 Mar 2019 17:34:59 -0700
From:   "Life is hard, and then you die" <ronald@...ovation.ch>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Henrik Rydberg <rydberg@...math.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Federico Lorenzi <federico@...velground.com>,
        linux-input <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] lib/hexdump.c: factor out generic hexdump
 formatting for reuse.


On Wed, Mar 27, 2019 at 09:46:48AM +0200, Andy Shevchenko wrote:
> On Wed, Mar 27, 2019 at 3:49 AM Ronald Tschalär <ronald@...ovation.ch> wrote:
> >
> > This introduces print_hex_dump_to_cb() which contains all the hexdump
> > formatting minus the actual printk() call, allowing an arbitrary print
> > function to be supplied instead. And print_hex_dump() is re-implemented
> > using print_hex_dump_to_cb().
> >
> > This allows other hex-dump logging functions to be provided which call
> > printk() differently or even log the hexdump somewhere entirely
> > different.
> 
> No Sign-off?

Yeah, my screwup.

> In any case, don't do it like this. smaller non-recursive printf() is
> better than one big receursive call.
> When it looks like an optimization, it's actually a regression.

Not sure where you see recursion here - are you referring to the
callback approach? Since dev_printk() ends up calling printk with a
dictionary as well as additional formatting, vs print_hex_dump()'s
stright use of printk, this seemed like the best way accommodate
various possible ways of logging the messages. But as per below I
guess this is moot.

> And yes, debugfs idea is not bad.

So it seems like that is the consensus. As per my other response, I'll
do this then and leave the print_hex_dump() alone.

> P.S. Also check %*ph specifier.

Thanks!


  Cheers,

  Ronald