linux-kernel - Re: [PATCH v3 1/5] seq_file: provide an analogue of print_hex

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Date:	Mon, 1 Sep 2014 13:49:41 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Tadeusz Struk <tadeusz.struk@...el.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Helge Deller <deller@....de>,
	Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Joe Perches <joe@...ches.com>, Marek Vasut <marex@...x.de>
Subject: Re: [PATCH v3 1/5] seq_file: provide an analogue of print_hex_dump()

Hi Andy,

On Mon, Sep 1, 2014 at 1:33 PM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>> >> However, to protect against overflows if hex_dump_to_buffer() ever changes,
>> >> I think it would be better to let hex_dump_to_buffer() indicate if the
>> >> passed buffer was to small (it already checks the passed linebuflen).
>> >> Then you can just check for that.
>> >
>> > I thought about that. We may introduce either new call and make
>> > current one the user of it or change all occurrences.
>> > Nevertheless, currently it will print only one groupsize if there is
>> > enough room for it but for two or more.
>> > Thus, I prefer to keep the behaviour "print until we can".
>>
>> The idea of seq_*() is that it will retry with a bigger bufsize if there's
>> not enough space.
>
> Fair enough.
>
> So, summarize above, the check before hex_dump_to_buffer() should care
> about maximum possible buffer needed for one line. But we have already
> rowsize calculated (we actually can't rely on groupsize in this case).
>
> Do you agree with formula rowsize * 3 + 2 + rowsize + 1?

That's the _current_ formula. The day hex_dump_to_buffer() is changed,
it will break silently.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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