linux-kernel - Re: [PATCH 2/3] Do not use acpi_device to find pci root bridge in

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Date:	Fri, 12 Oct 2012 18:54:25 +0800
From:	Jiang Liu <jiang.liu@...wei.com>
To:	Tang Chen <tangchen@...fujitsu.com>
CC:	<yinghai@...nel.org>, <lenb@...nel.org>, <bhelgaas@...gle.com>,
	<izumi.taku@...fujitsu.com>, <linux-acpi@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] Do not use acpi_device to find pci root bridge in
 _init code.

On 2012-10-12 18:42, Tang Chen wrote:
> On 10/12/2012 06:36 PM, Jiang Liu wrote:
>> On 2012-10-12 18:31, Tang Chen wrote:
>>> When the kernel is being initialized, and some hardwares are not added
>>> to system, there won't be acpi_device structs for these devices. But
>>> acpi_is_root_bridge() depends on acpi_device struct. As a result, all
>>> the not-added root bridge will not be judged as a root bridge in
>>> find_root_bridges(). And further more, no handle_hotplug_event_root()
>>> notifier will be installed for them.
>>>
>>> This patch introduces a new api to find all root bridges in system by
>>> getting HID directly from ACPI namespace, not depending on acpi_device
>>> struct.
>>>
>>> Signed-off-by: Tang Chen<tangchen@...fujitsu.com>
>>> ---
>>>   drivers/acpi/pci_root.c |   27 ++++++++++++++++++++++-----
>>>   1 files changed, 22 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>>> index 7d0fb03..3819bee 100644
>>> --- a/drivers/acpi/pci_root.c
>>> +++ b/drivers/acpi/pci_root.c
>>> @@ -128,9 +128,6 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
>>>   /**
>>>    * acpi_is_root_bridge - determine whether an ACPI CA node is a PCI root bridge
>>>    * @handle - the ACPI CA node in question.
>>> - *
>>> - * Note: we could make this API take a struct acpi_device * instead, but
>>> - * for now, it's more convenient to operate on an acpi_handle.
>>>    */
>>>   int acpi_is_root_bridge(acpi_handle handle)
>>>   {
>>> @@ -138,8 +135,28 @@ int acpi_is_root_bridge(acpi_handle handle)
>>>       struct acpi_device *device;
>>>
>>>       ret = acpi_bus_get_device(handle,&device);
>>> -    if (ret)
>>> -        return 0;
>>> +    if (ret) {
>>> +        /**
>>> +         * If a device is not added to the system yet, there won't be
>>> +         * an acpi_device struct for it. But it doesn't mean it is not
>>> +         * a PCI root bridge. In this case we need to get HID and CID
>>> +         * from ACPI namespace directly.
>>> +         */
>>> +        struct acpi_device_info *info;
>>> +        acpi_status status;
>>> +        status = acpi_get_object_info(handle,&info);
>>> +        if (ACPI_FAILURE(status)) {
>>> +            printk(KERN_ERR PREFIX "%s: Error reading"
>>> +                           "device info\n", __func__);
>>> +            return 0;
>>> +        }
>>> +
>>> +        ret = acpi_match_object_info_ids(info, root_device_ids);
>>> +        if (ret)
>>> +            return 0;
>>> +        else
>>> +            return 1;
>>> +    }
>> I have sent a similar patch to Yinghai before. For simplicity, we could
>> use acpi_match_object_info_ids() instead of acpi_match_device_ids()
>> directly.
> 
> Hum, I must have missed it. :)
> Using acpi_match_object_info_ids() directly seems good. I'm just worry
> about if it could cause any other problem. :)
> 
> So now, is this bug fixed ? And we don't need these patches, right ?
> 
> Thanks. :)
I think Yinghai has missed my patch too, so just suggest to use 
acpi_match_object_info_ids() directly.

--Gerry

> 
>> Thanks!
>> Gerry
>>
>>>
>>>       ret = acpi_match_device_ids(device, root_device_ids);
>>>       if (ret)
>>
>>
>> -- 
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>>
> 
> 
> .
> 


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