linux-kernel - Re: [PATCH 06/34] don't use __devexit_p to wrap hal2

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Date:	Fri, 02 Oct 2009 11:42:57 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH 06/34] don't use __devexit_p to wrap hal2_remove

At Fri, 2 Oct 2009 11:20:25 +0200,
Uwe Kleine-König wrote:
> 
> Hello,
> 
> On Fri, Oct 02, 2009 at 11:02:56AM +0200, Takashi Iwai wrote:
> > At Thu, 1 Oct 2009 10:53:55 +0200,
> > Uwe Kleine-König wrote:
> > > 
> > > On Thu, Oct 01, 2009 at 10:36:59AM +0200, Takashi Iwai wrote:
> > > > At Thu,  1 Oct 2009 10:28:10 +0200,
> > > > Uwe Kleine-König wrote:
> > > > > 
> > > > > The function hal2_remove is defined using __exit, so don't use __devexit_p
> > > > > but __exit_p to wrap it.
> > > > 
> > > > I think it's the other way round.  We should replace __exit with __devexit.
> > > > Ditto for sound/mips/sgio2audio.c.
> > > Actually both ways are possible.  I choosed the alternative that doesn't
> > > add bloat to the kernel.  The cost is that the device isn't hotplugable,
> > > but you can still unload the module to unbind the driver.
> > 
> > Hm, is it really safe to set remove=NULL although the driver needs
> > some work at unbinding?  It looks like that unbind is allowed no
> > matter whether remove is NULL or not.  So, it would jus keeps stray
> > resources, and it might conflict at the next bind.
> I just tried that and you're right.  IMHO that's a bug.  Greg?

I suppose it's a bug of the driver, not the core :)
If the driver doesn't need to release resources, it would work fine
with remove = NULL.  Also, the bus can provide a common remove
callback (even it's over the driver's remove callback).  So, in
theory, it can be NULL.

But, it must be really rare, and non-NULL remove is very likely a bug
if the driver is built with CONFIG_HOTPLUG=y...


thanks,

Takashi
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