linux-kernel - Re: [PATCH 01/18] char: moxa: call disable_pci_device() if pci

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Message-ID: <20100807095852.GX9031@bicker>
Date:	Sat, 7 Aug 2010 11:58:52 +0200
From:	Dan Carpenter <error27@...il.com>
To:	Vasiliy Kulikov <segooon@...il.com>
Cc:	kernel-janitors@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Alan Cox <alan@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rakib Mullick <rakib.mullick@...il.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/18] char: moxa: call disable_pci_device() if
	pci_probe() failed

On Sat, Aug 07, 2010 at 12:55:12PM +0400, Vasiliy Kulikov wrote:
> On Sat, Aug 07, 2010 at 09:22 +0200, Dan Carpenter wrote:
> > On Fri, Aug 06, 2010 at 11:49:10PM +0400, Kulikov Vasiliy wrote:
> > > Driver should call disable_pci_device() if it returns from pci_probe()
> > > with error. Also it must not be called if pci_request_region() fails as
> > > it means that somebody uses device resources and rules the device.
> > > 
> > 
> > I think we should disable it actually.  The comments on
> > pci_enable_device() and pci_disable_device() say that only the first and
> > last callers actually enable and disable it.  The others just increment
> > or decrement a counter.
> 
> See this thread: http://lkml.org/lkml/2005/2/13/82
> 
> Specifically this mail:
> 
>     Date    Mon, 14 Feb 2005 14:51:26 -0500
>     From    Jeff Garzik <>
> 
>     ...
>     You also need to consider situations such as out-of-tree drivers 
>     for the same hardware (might not use PCI API), and situations where you 
>     have peer devices discovered and used (PCI API doesn't have "hey, <this> 
>     device is associated with <current driver>, too" capability).
>     ...
> 
> Searching for 'pci_disable_device() inurl:lkml' doesn't give me newer info
> aboud this problem, so I think it's better to play safe.
> 

That's ancient.  That's a couple months before the start of git.

git show v2.6.12:drivers/pci/pci.c 

In those days pci_enable/disable_device() were not nestable.  These days
we can just unwind normally so it's a big improvement.

regards,
dan carpenter
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