linux-kernel - Re: [PATCH 1/2] drm: Only #define DEBUG if CONFIG_DYNAMIC

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Date:   Thu, 06 Dec 2018 08:22:46 -0800
From:   Joe Perches <joe@...ches.com>
To:     Michel Dänzer <michel@...nzer.net>,
        "Zhang, Jerry(Junwei)" <Jerry.Zhang@....com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Chris Wilson <chris@...is-wilson.co.uk>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] drm: Only #define DEBUG if CONFIG_DYNAMIC_DEBUG is
 disabled

On Thu, 2018-12-06 at 15:41 +0100, Michel Dänzer wrote:
> On 2018-12-06 1:23 p.m., Joe Perches wrote:
> > On Thu, 2018-12-06 at 12:52 +0100, Michel Dänzer wrote:
> > > In contrast to the 2b case, the pr_debug output isn't visible by default
> > > with 1b, so the latter doesn't fit "always produce output" either.
> > 
> > I think you are mistaken here.
> 
> Still puzzled as to what you're hoping to achieve with that kind of
> language. None of the confusion about this patch has been on my part. :)

Doubtful.

> > Adding #define DEBUG as Chris did enables pr_debug output
> > and is your 1b.
> > 
> > Perhaps your default console logging level is set to a
> > non-default value.
> 
> I have CONFIG_DYNAMIC_DEBUG enabled in my kernels. The problem addressed
> by this patch is that messages from drm_debug_printer are visible by
> default (case 2b), whereas they shouldn't be (case 2a, like 1b).

The default for config_dynamic_debug when DEBUG is defined is
to output the message equivalent to when DEBUG is defined and
config_dynamic_debug is not.

That's a good thing and has been the general default since 2011.

You want to override that, I suppose that's OK but it's
definitely not a _fix_ as you have written.

It's just a change in behavior.

You added a "Fixes:" line.  I believe that wrong.

A long time ago, at my suggestion:

commit b558c96ffa53f4b3dd52b774e4fb7a52982ab52b
Author: Jim Cromie <jim.cromie@...il.com>
Date:   Mon Dec 19 17:11:18 2011 -0500

    dynamic_debug: make dynamic-debug supersede DEBUG ccflag
    
    If CONFIG_DYNAMIC_DEBUG is defined, honor it over DEBUG, so that
    pr_debug()s are controllable, instead of always-on.  When DEBUG is
    also defined, change _DPRINTK_FLAGS_DEFAULT to enable printing by
    default.

cheers, Joe