linux-kernel - Re: [PATCH v3] PCI: Only enable IO window if supported

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Date:	Wed, 05 Aug 2015 19:22:44 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH v3] PCI: Only enable IO window if supported

On 08/05/2015 06:38 PM, Yinghai Lu wrote:
> On Wed, Aug 5, 2015 at 6:14 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>>
>> It only can avoid warning with bridge, and still have warning on
>> devices under the bridge.
>>
>> also would have problem on transparent bridges, like
>>
>> BRIDGE_A ---- BRIDGE_AA----DEVICE_AA
>>                     |
>>                     \-- BRIDGE_AB ---DEVICE_AB
>>
>> if only BRIDGE_A and BRIDGE_AA are transparent, and BRIDGE_AB is not.
>>
>> and if pci_bridge_supports_io() return false for BRIDGE_A.
>>
>> We will have all three bridges have PCI_BUS_FLAGS_SUPPORTS_IO cleared.
>> so all will not been sized and will not get assigned io port resource.
>>
>> later DEVICE_AA could root bus io port as parent, and get io resource assigned.
>> but DEVICE_AB will not get assigned.
>>
>> so we should get rid of pci_bridge_supports_io(), and just check root
>> resource IO port.
>
> I would suggest this version instead:
>
> Subject: [PATCH] PCI: Only try to assign io port only if root bus support that
>

Bjorn had asked me to move the IO support check out of pci_bridge_check_ranges().
It looks like you want to keep it there.

Can you explain your reasons ? Sorry, I just don't understand.

Guenter

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