linux-kernel - Re: [PATCH v1 1/5] seq_file: provide an analogue of print_hex

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Date:	Thu, 10 Jul 2014 12:50:39 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Marek Vasut <marex@...x.de>
Cc:	Joe Perches <joe@...ches.com>,
	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>,
	linux390@...ibm.com, Alexander Viro <viro@...iv.linux.org.uk>,
	qat-linux@...el.com, linux-crypto@...r.kernel.org,
	linux-media@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/5] seq_file: provide an analogue of print_hex_dump()

On Thu, 2014-07-10 at 09:58 +0200, Marek Vasut wrote:
> On Wednesday, July 09, 2014 at 11:21:08 PM, Joe Perches wrote:
> > On Wed, 2014-07-09 at 22:39 +0200, Marek Vasut wrote:
> > > The above function looks like almost verbatim copy of print_hex_dump().
> > > The only difference I can spot is that it's calling seq_printf() instead
> > > of printk(). Can you not instead generalize print_hex_dump() and based
> > > on it's invocation, make it call either seq_printf() or printk() ?
> > 
> > How do you propose doing that given any seq_<foo> call
> > requires a struct seq_file * and print_hex_dump needs
> > a KERN_<LEVEL>.
> 
> I can imagine a rather nasty way, I can't say I would like it myself tho. The 
> general idea would be to pull out the entire switch {} statement into a separate 
> functions , one for printk() and one for seq_printf() cases. Then, have a 
> generic do_hex_dump() call which would take as an argument a pointer to either 
> of those functions and a void * to either the seq_file or level . Finally, there 
> would have to be a wrapper to call the do_hex_dump() with the correct function 
> pointer and it's associated arg.
> 
> Nasty? Yes ... Ineffective? Most likely.

It looks not good idea, yeah.

> > Is there an actual value to it?
> 
> Reducing the code duplication, but I wonder if there is a smarter solution than 
> the horrid one above.

I have considered to modify hex_dump_to_buffer() to return how many
bytes it actually proceed to the buffer. In that case we can directly
print to m->buf like other seq_<foo> calls do.

But I still have doubts about it. Any opinion?

-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy

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