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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Toshi Kani <toshi.kani@hp.com>
Cc: ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>, Yinghai Lu <yinghai@kernel.org>
Subject: Re: [PATCH 2/3] ACPI / hotplug: Fix PCI host bridge hot removal
Date: Mon, 18 Nov 2013 22:39:25 +0100
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On Monday, November 18, 2013 11:10:05 AM Toshi Kani wrote:
> On Thu, 2013-11-14 at 00:16 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > 
> > Since the PCI host bridge scan handler does not set hotplug.enabled,
> > the check of it in acpi_bus_device_eject() effectively prevents the
> > root bridge hot removal from working after commit a3b1b1ef78cd
> > (ACPI / hotplug: Merge device hot-removal routines).  However, that
> > check is not necessary, because the other acpi_bus_device_eject()
> > users, acpi_hotplug_notify_cb and acpi_eject_store(), do the same
> > check by themselves before executing that function.
> > 
> > For this reason, remove the scan handler check from
> > acpi_bus_device_eject() to make PCI hot bridge hot removal work
> > again.
> 
> I am curious why the PCI host bridge scan handler does not set
> hotplug.enabled.  Is this how it disables hotplug via sysfs eject but
> enables via ACPI notification? 

It just doesn't register for hotplug at all.  I guess it could set that
bit alone, but then it would be quite confusing and the check is not
necessary anyway.

Thanks,
Rafael