linux-kernel - Re: [PATCH 01/44] kernel: Add support for poweroff handler call chain

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Date:	Thu, 9 Oct 2014 08:38:36 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Pavel Machek <pavel@....cz>
Cc:	linux-kernel@...r.kernel.org,
	adi-buildroot-devel@...ts.sourceforge.net,
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	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Romain Perier <romain.perier@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>,
	Alexander Graf <agraf@...e.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 01/44] kernel: Add support for poweroff handler call chain

On Thu, Oct 09, 2014 at 12:31:43PM +0200, Pavel Machek wrote:
> Hi!
> 
> > +/**
> > + *	register_poweroff_handler_simple - Register function to be called to power off
> > + *					   the system
> > + *	@handler:	Function to be called to power off the system
> > + *	@priority:	Handler priority. For priority guidelines see
> > + *			register_poweroff_handler.
> > + *
> > + *	This is a simplified version of register_poweroff_handler. It does not
> > + *	take a notifier as argument, but a function pointer. The function
> > + *	registers a poweroff handler with specified priority. Poweroff
> > + *	handlers registered with this function can not be unregistered,
> > + *	and only a single poweroff handler can be installed using it.
> > + *
> > + *	This function must not be called from modules and is therefore
> > + *	not exported.
> > + *
> > + *	Returns -EBUSY if a poweroff handler has already been registered
> > + *	using register_poweroff_handler_simple. Otherwise returns zero,
> > + *	since atomic_notifier_chain_register() currently always returns zero.
> > + */
> > +int register_poweroff_handler_simple(void (*handler)(void), int priority)
> > +{
> > +	char symname[KSYM_NAME_LEN];
> > +
> > +	if (poweroff_handler_data.handler) {
> > +		lookup_symbol_name((unsigned long)poweroff_handler_data.handler,
> > +				   symname);
> > +		pr_warn("Poweroff function already registered (%s)", symname);
> > +		lookup_symbol_name((unsigned long)handler, symname);
> > +		pr_cont(", cannot register %s\n", symname);
> > +		return -EBUSY;
> > +	}
> 
> Dunno, are you maybe overdoing the debugging infrastructure a bit?
> This is not going to happen in production, and if it does happen,
> developer can look the symbol name himself.

On the other side, I don't think it hurts to have that message.
Anyway, I'll use %ps as suggested by Geert.

Guenter
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