linux-kernel - Re: [RFC PATCH v2, part 2 09/18] PCI, PPC: use hotplug-safe iterators to walk PCI buses

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Date:	Wed, 15 May 2013 23:07:51 +0800
From:	Liu Jiang <liuj97@...il.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Bill Pemberton <wfp5p@...ginia.edu>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH v2, part 2 09/18] PCI, PPC: use hotplug-safe iterators
 to walk PCI buses

On 05/15/2013 07:30 AM, Benjamin Herrenschmidt wrote:
> On Wed, 2013-05-15 at 00:51 +0800, Jiang Liu wrote:
>> Enhance PPC architecture specific code to use hotplug-safe iterators
>> to walk PCI buses.
> I was about to ack it but then I saw:
>
>> diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
>> index 51a133a..a41c6dd 100644
>> --- a/arch/powerpc/kernel/pci_64.c
>> +++ b/arch/powerpc/kernel/pci_64.c
>> @@ -208,7 +208,6 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
>>   			  unsigned long in_devfn)
>>   {
>>   	struct pci_controller* hose;
>> -	struct list_head *ln;
>>   	struct pci_bus *bus = NULL;
>>   	struct device_node *hose_node;
>>   
>> @@ -229,18 +228,16 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
>>   	/* That syscall isn't quite compatible with PCI domains, but it's
>>   	 * used on pre-domains setup. We return the first match
>>   	 */
>> -
>> -	for (ln = pci_root_buses.next; ln != &pci_root_buses; ln = ln->next) {
>> -		bus = pci_bus_b(ln);
>> -		if (in_bus >= bus->number && in_bus <= bus->busn_res.end)
>> +	for_each_pci_root_bus(bus)
>> +		if (in_bus >= bus->number && in_bus <= bus->busn_res.end &&
>> +		    bus->dev.of_node)
>>   			break;
>> -		bus = NULL;
>> -	}
>> -	if (bus == NULL || bus->dev.of_node == NULL)
>> +	if (bus == NULL)
>>   		return -ENODEV;
> You just removed the NULL check for the of_node field...
Hi Benjamin,
     Thanks for review.
     I just moved the "bus->dev.of_node == NULL" into the above 
for_each_pci_root_bus()
loop:)
     Will send you another version according to your suggestion to use 
pci_bus_to_host()
to simplify the code.
Regards!
Gerry

>   
>>   	hose_node = bus->dev.of_node;
>>   	hose = PCI_DN(hose_node)->phb;
> Which is dereferrenced here.	
>
>> +	pci_bus_put(bus);
> On the other hand, the whole thing can probably be using
> pci_bus_to_host() instead.... the above code is bitrotted.
>
>>   	switch (which) {
>>   	case IOBASE_BRIDGE_NUMBER:
>   
> Cheeers,
> Ben.
>
>

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