linux-kernel - Re: [PATCH v2] [media] v4l: omap4iss: Add DEBUG compiler flag

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Date:	Thu, 06 Mar 2014 02:52:03 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Paul Bolle <pebolle@...cali.nl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] [media] v4l: omap4iss: Add DEBUG compiler flag

Hi Joe,

On Wednesday 05 March 2014 17:35:42 Joe Perches wrote:
> On Thu, 2014-03-06 at 02:27 +0100, Laurent Pinchart wrote:
> > On Wednesday 05 March 2014 17:00:37 Joe Perches wrote:
> > > On Thu, 2014-03-06 at 01:48 +0100, Laurent Pinchart wrote:
> > > > Would you recommend to drop driver-specific Kconfig options related to
> > > > debugging and use CONFIG_DYNAMIC_DEBUG instead ?
> > > 
> > > For development, sure, if there's sufficient memory.
> > > For embedded systems with limited memory, using dynamic_debug isn't
> > > always possible or effective.
> > > Also, there are sometimes reasons to have debugging messages always
> > > enabled or emitted.
> > > For those cases, either adding #define DEBUG or using printk(KERN_DEBUG
> > > would be fine.
> > 
> > My goal here is to offer an easy way for users to enable debugging without
> > requiring changes to the source code.
> 
> Dynamic debugging works, but various distributions don't
> have it enabled.
> 
> > The driver includes various dev_dbg() messages, I don't want to ask people
> > reporting problems to turn them into printk() calls :-) Even adding
> > #define DEBUG at the beginning of the source files is likely too error
> > prone for users without much programming experience.
>
> I think your best bet is to add #define DEBUG to a common
> header file like iss.h or omap4iss.h

I've thought about that, but it would require iss.h to be included before all 
other headers. I've also thought about creating an iss-debug.h header to be 
included first just to #define DEBUG, but decided to go for handling the OMAP4 
ISS debug option in the Makefile instead. If that's ugly and discouraged as 
reported by Mauro I can try to come up with something else.

-- 
Regards,

Laurent Pinchart

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