linux-kernel - Re: [PATCH v2 35/37] PCI: Make /sys/bus/pci/rescan rescan root

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Message-ID: <CAE9FiQXwk8MhaaHB=yF78GKzZeGDvjXwCdryN=xFzTkM9FS5FQ@mail.gmail.com>
Date:	Mon, 12 Mar 2012 23:26:40 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 35/37] PCI: Make /sys/bus/pci/rescan rescan root

On Mon, Mar 12, 2012 at 8:44 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Sat, Mar 10, 2012 at 12:00 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>> It will rediscover removed pci root buses.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> ---
>>  drivers/pci/pci-sysfs.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
>> index 4d122cb..fc0a7de 100644
>> --- a/drivers/pci/pci-sysfs.c
>> +++ b/drivers/pci/pci-sysfs.c
>> @@ -284,6 +284,7 @@ msi_bus_store(struct device *dev, struct device_attribute *attr,
>>
>>  #ifdef CONFIG_HOTPLUG
>>  static DEFINE_MUTEX(pci_remove_rescan_mutex);
>> +void __weak arch_pci_root_rescan(void) { }
>>  static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
>>                                size_t count)
>>  {
>> @@ -295,6 +296,7 @@ static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
>>
>>        if (val) {
>>                mutex_lock(&pci_remove_rescan_mutex);
>> +               arch_pci_root_rescan();
>>                while ((b = pci_find_next_bus(b)) != NULL)
>>                        pci_rescan_bus(b);
>>                mutex_unlock(&pci_remove_rescan_mutex);
>
> This is gross.  We used to rescan every previously-discovered PCI root bus.
>
> Now, we do the same, plus:
> 1) Scan the ACPI namespace for PCI host bridges, adding and scanning
> any we haven't seen before, and
> 2) scan domain 0, buses 0 - pcibios_last_bus, looking for any we
> haven't seen before.

to have /sys/bus/pci/scan_root again?

Yinghai
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