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

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Date:	Thu, 06 Mar 2014 11:55:31 +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 19:25:47 Joe Perches wrote:
> On Thu, 2014-03-06 at 02:52 +0100, Laurent Pinchart wrote:
> > 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.
> 
> Unless debugging logging statements are in system level static inlines,
> adding #define DEBUG to iss.h should otherwise produce the same output
> as -DDEBUG in a Makefile.

dev_dbg() is defined in include/linux/device.h as

#if defined(CONFIG_DYNAMIC_DEBUG)
#define dev_dbg(dev, format, ...)                    \
do {                                                 \
        dynamic_dev_dbg(dev, format, ##__VA_ARGS__); \
} while (0)
#elif defined(DEBUG)
#define dev_dbg(dev, format, arg...)            \
        dev_printk(KERN_DEBUG, dev, format, ##arg)
#else
#define dev_dbg(dev, format, arg...)                            \
({                                                              \
        if (0)                                                  \
                dev_printk(KERN_DEBUG, dev, format, ##arg);     \
        0;                                                      \
})
#endif

We thus need the #define DEBUG it appear before the first time device.h is 
included, either directly or indirectly. Adding #define DEBUG to iss.h won't 
work now as iss.h is included after all system includes (which is the usual 
practice, #include <...> come before #include "...").

-- 
Regards,

Laurent Pinchart

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