linux-kernel - Re: [PATCH 02/23] PCI, sysfs: create rescan_bridge under /sys/.../pci/devices/... for pci bridges

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Date:	Thu, 8 Mar 2012 22:42:51 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 02/23] PCI, sysfs: create rescan_bridge under
 /sys/.../pci/devices/... for pci bridges

On Thu, Mar 8, 2012 at 4:52 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Tue, Mar 6, 2012 at 12:13 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>> Current code will create rescan for every pci device under parent bus.
>> that is not right. the device is already there, there is no reason to rescan it.
>>
>> We could have rescan for pci bridges. less confusing.
>
> Yes, but now we have *three* rescan attributes for a single bridge/bus:
>
>    /sys/devices/pci0000:00/0000:00:01.0/pci_bus/0000:01/rescan

no, that one is not there, and should not be added.

But I do suggest to add
/sys/devices/pci0000:00/0000:00:01.0/pci_bus/0000:01/remove

>    /sys/devices/pci0000:00/0000:00:01.0/rescan_bridge
>    /sys/devices/pci0000:00/0000:00:01.0/rescan
>
> and this for an endpoint:
>
>    /sys/devices/pci0000:00/0000:00:05.0/rescan
>
> I think endpoints should not have a "rescan" attribute at all, and
> bridges should have only a "rescan" attribute (not "rescan" and
> "rescan_bridge").

agreed,  that rescan actually is doing rescan of it's parent bus.

I have suggested to remove it. but Alex said some HP internal
application will need
that, so it can not be removed.

at last I have to use rescan_bridge for bridge device.

>
> I'm not sure about "pci_bus/.../rescan".  I know you didn't add that,
> but I'm not sure it makes sense to have both that and a "rescan" on
> the bridge device.  If we have both, what's the difference between
> them?

rescan : for device parent bus, that is really weird.
rescan_bridge: will only show up that device is bridge, and rescan that bridge.

Yinghai
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