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Subject: RFC: dynamic debug enhancements?
From: Joe Perches <joe@perches.com>
To: Jason Baron <jbaron@redhat.com>
Cc: Jim Cromie <jim.cromie@gmail.com>, LKML <linux-kernel@vger.kernel.org>
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Date: Sun, 21 Aug 2011 17:15:43 -0700
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Hey Jason.

I recently went through drivers/media and updated
lots of calls to pr_<level>.

A common pattern for debugging there and elsewhere
treewide is the use of macros like:

#define dprintk(level, fmt, ...)			\
do {							\
	if (level > [some_modparam_var])		\
		pr_debug(fmt, ##__VA_ARGS__);		\
} while (0)

and

#define dprintk(mask, fmt, ...)				\
do {							\
	if (mask & [some_modparam_var])			\
		pr_debug(fmt, ##__VA_ARGS__);		\
} while (0)

It might be useful to have standardized calls
like pr_debug_level and pr_debug_mask instead
of multiple hand-rolled variants treewide.

Another common thing was the use of various
__FILE__, __func__, __LINE__ outputs.

I think __FILE__ is not particularly useful and
can reasonably be replaced by KBUILD_MODNAME.

Perhaps it would be good to have options to
enable these outputs with specific controls
for dynamic_debug uses.

Maybe something like using a define similar to
pr_fmt for what options are preselected for
various ddebug outputs like:

#define DYNAMIC_DEBUG_DEFAULT_FLAGS 		\
	(_DPRINTK_FLAGS_INCL_MODNAME |		\
	 _DPRINTK_FLAGS_INCL_FUNCNAME |		\
	 _DPRINTK_FLAGS_INCL_LINENO)