linux-kernel - Re: [PATCH 2/3] staging: vme: add struct vme

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Message-ID: <20110829235508.GA30400@flamenco.cs.columbia.edu>
Date:	Mon, 29 Aug 2011 19:55:08 -0400
From:	"Emilio G. Cota" <cota@...ap.org>
To:	Greg KH <greg@...ah.com>, Manohar Vanga <manohar.vanga@...n.ch>
Cc:	gregkh@...e.de, martyn.welch@...com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] staging: vme: add struct vme_dev for VME devices

On Mon, Aug 29, 2011 at 10:52:41 -0700, Greg KH wrote:
> On Mon, Aug 29, 2011 at 11:02:49AM +0200, Manohar Vanga wrote:
> > --- a/drivers/staging/vme/vme_bridge.h
> > +++ b/drivers/staging/vme/vme_bridge.h
> > @@ -115,9 +115,8 @@ struct vme_bridge {
> >  	struct list_head bus_list; /* list of VME buses */
> >  	struct module *owner;	/* module that owns the bridge */
> >  
> > -	struct device dev[VME_SLOTS_MAX];	/* Device registered with
> > -						 * device model on VME bus
> > -						 */
> > +	struct vme_dev dev[VME_SLOTS_MAX];	/* Device registered
> > +						 * on VME bus */
> 
> Overall, this is the right way to go, using a vme_dev.
> 
> BUT, you should never have a static list of devices, these should be
> pointers, not actual structures here, otherwise your reference counting
> just got all messed up and is wrong.
> 
> And yes, I know you didn't create the code this way, but it needs to be
> fixed _before_ you make this kind of a change.

True, I overlooked this while reviewing >_<

Manohar, have a look at vme_unregister_driver_ng() and
__vme_register_driver_bus() in this patch:
 
    http://article.gmane.org/gmane.linux.kernel/1054046

Note that there's no kfree(vme_dev) in those functions. put_device(),
which is also called from device_unregister(), decrements
the underlying kobj's refcount. When this refcount reaches 0,
kobject_release() is called. Eventually dev->release() gets called,
which in this case is set to vme_dev_release_ng(); it's there
(and only there) where vme_dev can be freed.

		Emilio
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