linux-kernel - Re: [PATCH v4 08/12] PCI: Introduce /sys/bus/pci/devices/.../remove

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Date:	Thu, 19 Mar 2009 14:46:46 -0600
From:	Alex Chiang <achiang@...com>
To:	Trent Piepho <xyzzy@...akeasy.org>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 08/12] PCI: Introduce /sys/bus/pci/devices/.../remove

* Trent Piepho <xyzzy@...akeasy.org>:
> On Thu, 19 Mar 2009, Alex Chiang wrote:
> > * Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>:
> > >> +	pci_remove_bus_device(pdev);
> > >> +	if (bridge && list_empty(&pdev->bus->devices))
> > >> +		pci_remove_bus(pdev->bus);
> > >
> > > I cannot understand the above two lines. Could you explain
> > > what it intend?
> >
> > If the user says:
> >
> > 	echo 1 > /sys/bus/pci/devices/.../remove
> >
> > And that device is a bridge, then we need to specifically call
> > pci_remove_bus as well, to actually remove the bus itself.
> > Without it, pci_bus_remove_device() will remove all of its
> > children (and subordinate buses) in a depth-first manner, but we
> > will never actually remove the bus that the user specified.
> 
> Did this end up being the source of the pci resource assignment warnings
> that were produced when re-adding a bridge that was removed?

I think that was one reason. I found that it was necessary during
multiple remove/rescan cycles; after the 2nd rescan, we had a
stale pci_bus hanging around that was manifesting itself as a
sysfs issue.

The other thing that Kenji found was in pci_setup_bridge(), where
we don't want to initialize the BARs if the bridge has already
been added.

Thanks.

/ac

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