linux-kernel - Re: [PATCH v2 03/15] drivers: thermal: tsens: Add __func_

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Date:   Thu, 29 Aug 2019 16:19:12 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        Andy Gross <agross@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Brian Masney <masneyb@...tation.org>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 03/15] drivers: thermal: tsens: Add __func__
 identifier to debug statements

On Thu, Aug 29, 2019 at 07:58:45PM +0530, Amit Kucheria wrote:
> On Thu, Aug 29, 2019 at 7:35 PM Daniel Thompson
> <daniel.thompson@...aro.org> wrote:
> >
> > On Tue, Aug 27, 2019 at 05:43:59PM +0530, Amit Kucheria wrote:
> > > Printing the function name when enabling debugging makes logs easier to
> > > read.
> > >
> > > Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> > > Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> > > Reviewed-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> >
> > This should need to be manually added at each call site; it is already
> > built into the logging system (the f flag for dynamic debug)?
> 
> I assume you meant "shouldn't".

Quite so. Sorry about that.


> I haven't yet integrated dynamic debug into my daily workflow.
> 
> Last time I looked at it, it was a bit bothersome to use because I
> needed to lookup exact line numbers to trigger useful information. And
> those line numbers constantly keep changing as I work on the driver,
> so it was a bit painful to script. Not to mention the syntax to frob
> the correct files in debugfs to enable this functionality.
> 
> As opposed to this, adding the following to the makefile is so easy. :-)
> 
> CFLAGS_tsens-common.o          := -DDEBUG
> 
> Perhaps I am using it all wrong? How would I go about using dynamic
> debug instead of this patch?

Throwing dyndbg="file <fname>.c +pf" onto the kernel command line is a
good start (+p enables debug level prints, +f causes messages to include
the function name).

When the C files map to module names (whether the modules are actually
built-in or not) then <module>.dyndbg=+pf is a bit cleaner and allows
you to debug the whole of a driver without how it is decomposed into
files.

There are (many) other controls to play with[1] but the above should be
sufficient to simulate -DDEBUG .


Daniel.

[1]
https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html