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

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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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