linux-kernel - Re: [PATCH] SH/Dreamcast - fix regressions, whitespace and memory leaks in Maple Bus driver

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Date:	Mon, 4 Feb 2008 20:57:59 -0800
From:	Greg KH <greg@...ah.com>
To:	Adrian McMenamin <adrian@...golddream.dyndns.info>
Cc:	Paul Mundt <lethal@...ux-sh.org>,
	linux-sh <linux-sh@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] SH/Dreamcast - fix regressions, whitespace and memory
	leaks in Maple Bus driver

On Mon, Feb 04, 2008 at 10:37:37PM +0000, Adrian McMenamin wrote:
> 
> On Mon, 2008-02-04 at 08:14 -0800, Greg KH wrote:
> > On Mon, Feb 04, 2008 at 08:27:55AM +0000, Adrian McMenamin wrote:
> > > 
> > > On Sun, 2008-02-03 at 21:29 -0800, Greg KH wrote:
> > > > On Sun, Feb 03, 2008 at 08:00:47PM +0000, Adrian McMenamin wrote:
> > > > > From: Adrian McMenamin
> > > > > 
> > > > > This patch fixes the regression noted here:
> > > > > http://lkml.org/lkml/2008/1/26/189 as well as whitespace issues in the
> > > > > previous commit of this driver and the memory leaks noted here:
> > > > > http://lkml.org/lkml/2008/2/2/143 (as well as one or two other minor
> > > > > cleanups).
> > > > 
> > > > Which portion of the patch fixes the kobject WARN_ON()?
> > > 
> > > 
> > > 
> > > +	if (mdev->registered == 0) {
> > > +		retval = device_register(&mdev->dev);
> > > +		if (retval) {
> > > +			printk(KERN_INFO
> > > +			"Maple bus: Attempt to register device"
> > > +			" (%x, %x) failed.\n",
> > > +			mdev->port, mdev->unit);
> > > +			maple_free_dev(mdev);
> > > +			mdev = NULL;
> > > +			return;
> > > +		}
> > > +		mdev->registered = 1;
> > > +	}
> > >  }
> > > 
> > > 
> > > Specifically the check on mdev->registered
> > 
> > So the code path could cause devices to be registered more than once?
> > That seems broken, as no other bus that I know of needs such a check :(
> > 
> > Is there a way to fix the root problem here, instead of this type of
> > change?
> > 
> 
> The hardware is very flaky. If I add in delays to the bus start, it will
> detect the devices, but it's not brilliant. Registering an empty device
> got round that problem, at the price of testing for the earlier
> registration.

That sounds like you are just papering over the problem.  Just delay
and let the hardware settle down if needed :)

thanks,

greg k-h
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