linux-kernel - Re: [RFC 1/2] printk/dynamic_debug: Remove cyclic dependency between printk.h and dynamic

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Date:   Wed, 12 Jan 2022 20:38:57 -0700
From:   jim.cromie@...il.com
To:     Petr Mladek <pmladek@...e.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Chris Down <chris@...isdown.name>,
        Marc Zyngier <maz@...nel.org>,
        Andrew Scull <ascull@...gle.com>,
        Will Deacon <will@...nel.org>, Jason Baron <jbaron@...mai.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: [RFC 1/2] printk/dynamic_debug: Remove cyclic dependency between
 printk.h and dynamic_debug.h

On Wed, Jan 12, 2022 at 5:12 AM Petr Mladek <pmladek@...e.com> wrote:
>
> On Tue 2022-01-11 17:01:35, Rasmus Villemoes wrote:
> > On 11/01/2022 15.30, Petr Mladek wrote:


> > >  static inline int dynamic_debug_exec_queries(const char *query, const char *modname)
> > >  {
> > > -   pr_warn("kernel not built with CONFIG_DYNAMIC_DEBUG_CORE\n");
> > > +   /* Use raw _printk() to avoid cyclic dependency. */
> > > +   _printk(KERN_WARNING "kernel not built with CONFIG_DYNAMIC_DEBUG_CORE\n");
> > >     return 0;
> > >  }
> >
> > And for this one I think the solution is even simpler, as I can't find
> > any in-tree callers. Perhaps just nuke it entirely?
>
> Adding Jim into Cc whether he still has any plans to use this API.
>
> Best Regards,
> Petr

This EXPORT can go.

For the user I envisioned, DRM, Ive done it with a callback
provided by dynamic-debug, which maps bits in __drm_debug,
to calls to ddebug_exec_queries, without the export.

https://lore.kernel.org/lkml/20220107052942.1349447-19-jim.cromie@gmail.com/

This seems like a narrower/tighter interface,
and readily repeatable for other users, should they emerge.

Id welcome your inputs on the whole patchset.
Rasmus, I extend your Factory macros to add a .class_id
and use them to wrap __drm_dev_dbg etc

thanks