Date: Mon, 14 Feb 2005 20:50:04 +0100
Message-ID: <s5h650udiqb.wl@alsa2.suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Greg KH <greg@kroah.com>
Cc: Jeff Garzik <jgarzik@pobox.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: avoiding pci_disable_device()...
In-Reply-To: <20050214193413.GA10231@kroah.com>
References: <4210021F.7060401@pobox.com>
	<20050214190619.GA9241@kroah.com>
	<s5h7jlbc5ci.wl@alsa2.suse.de>
	<20050214193413.GA10231@kroah.com>
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At Mon, 14 Feb 2005 11:34:13 -0800,
Greg KH wrote:
> 
> On Mon, Feb 14, 2005 at 08:24:29PM +0100, Takashi Iwai wrote:
> > At Mon, 14 Feb 2005 11:06:19 -0800,
> > Greg KH wrote:
> > > 
> > > > As a result, I have committed the attached patch to libata-2.6.  In many 
> > > > cases, it is a "semantic fix", addressing the case
> > > > 
> > > > 	* pci_request_regions() indicates hardware is in use
> > > > 	* we rudely disable the in-use hardware
> > > > 
> > > > that would not occur in practice.
> > > > 
> > > > But better safe than sorry.  Code cuts cut-n-pasted all over the place.
> > > > 
> > > > I'm hoping one or two things will happen now:
> > > > * janitors fix up the other PCI drivers along these lines
> > > > * improve the PCI API so that pci_request_regions() is axiomatic
> > > 
> > > Do you have any suggestions for how to do this?
> > 
> > How about to add an exclusiveness check in pci_enable_device()?
> > Most drivers suppose that the given pci resources are exclusively
> > available.
> 
> You mean only allow pci_enable_device() to work for the first caller of
> it?  I don't see how that would help this issue out.

Well, for example, add a new pointer to indicate the driver accessing
exclusively.  And pci_enable_device() (maybe a new variant would be
better for compatibility) checks whether this is free.

The second caller wouldn't reach even to pci_request_regions() because
of this check.  So, no side-effect of pci_disable_device() in the
error path.


Takashi
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