Re: [PATCH V2 0/2] OMAPDSS: Enable dynamic debug printing

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Thu, 2012-09-27 at 16:20 +0530, Mahapatra, Chandrabhanu wrote:
> On Wed, Sep 26, 2012 at 7:59 PM, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:
> 
> > This doesn't work quite correctly. The problem is in dss.h, where we
> > define DEBUG if CONFIG_OMAP2_DSS_DEBUG_SUPPORT is set. The thing is,
> > DEBUG should be defined before including the kernel headers where the
> > pr_debug etc are defined.
> >
> > So if you try the patches without dynamic debugging enabled, you won't
> > get any debug outputs at all, even if CONFIG_OMAP2_DSS_DEBUG_SUPPORT is
> > set.
> >
> > And for dynamic debug, the Kconfig help says:
> >
> > If a source file is compiled with DEBUG flag set, any
> > pr_debug() calls in it are enabled by default, but can be
> > disabled at runtime as below.  Note that DEBUG flag is
> > turned on by many CONFIG_*DEBUG* options.
> >
> > So if we have CONFIG_OMAP2_DSS_DEBUG_SUPPORT set, all the pr_debugs
> > should be enabled by default, which is not the case, again because DEBUG
> > is defined too late.
> >
> > I think setting DEBUG in dss.h should be removed, and instead DEBUG
> > should be set in the makefile if CONFIG_OMAP2_DSS_DEBUG_SUPPORT is set.
> >
> >  Tomi
> >
> 
> Well the documentation lags in describing about the DEBUG flag. I
> should have checked DYNAMIC_DEBUG in Kconfig and pr_debug definition
> in printk.h file.
> 
> #if defined(CONFIG_DYNAMIC_DEBUG)
> /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */
> #define pr_debug(fmt, ...) \
>         dynamic_pr_debug(fmt, ##__VA_ARGS__)
> #elif defined(DEBUG)
> #define pr_debug(fmt, ...) \
>         printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> #else
> #define pr_debug(fmt, ...) \
>         no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> #endif
> 
> As per the definition above pr_debug is dynamic with
> CONFIG_DYNAMIC_DEBUG set or else with DEBUG set it is just a normal
> kernel debug printk as you have mentioned.
> I still don't get how even if DEBUG is set before DSSDBG() is defined
> in dss.c pr_debug() fails to enable.

Because printk.h is included without DEBUG, thus pr_debug is defined as
no_printk.

> Well anyways, how to do the same in the Makefile? I tried adding
> ccflags-$(CONFIG_OMAP2_DSS_DEBUG_SUPPORT) += -DEBUG
> to makefile in dss directory but of no use.

-D option for the compiler is used to set defines. So it should be
-DDEBUG

 Tomi


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