Re: [KJ] question about pci_dev_put

[Greg KH <greg@kroah.com>]

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On Thu, May 18, 2006 at 01:16:22AM +0200, trem wrote:
> Hi
> 
> I'm looking for information about pci_get_device and pci_dev_put. If my
> research are good,
> I've understood that pci_get_device increment the counter of the device
> returned, and it also
> decremented the counter of the device given as "from".
> 
> I've searched example in the source. I've found this one in
> arch/ppc/platforms/85xx/mpc85xx_cds_common.c(git kernel) :
> 
>     if ((dev = pci_get_device(PCI_VENDOR_ID_VIA,
>                                         PCI_DEVICE_ID_VIA_82C586_2,
> NULL))) {
>                 dev->irq = 10;
>                 pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 10);
>         pci_dev_put(dev);
>         }
> 
>     if ((dev = pci_get_device(PCI_VENDOR_ID_VIA,
>                                         PCI_DEVICE_ID_VIA_82C586_2, dev))) {
>                 dev->irq = 11;
>                 pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 11);
>         pci_dev_put(dev);
>         }
> 
> So, if I don't mistake, this code is buggy, the counter is decremented
> twice in the second if.
> One in the pci_get_device and one in pci_dev_put. I'm on the right way ?

Yes, the code is incorrect.  Here's a proper fix for it.  Kumar, feel
free to apply.

-------

From: Greg Kroah-Hartman <gregkh@suse.de>
Subject: Fix incorrect pci reference counting in 85xx code

As pointed out by trem <tremyfr@yahoo.fr>

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 arch/ppc/platforms/85xx/mpc85xx_cds_common.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- gregkh-2.6.orig/arch/ppc/platforms/85xx/mpc85xx_cds_common.c
+++ gregkh-2.6/arch/ppc/platforms/85xx/mpc85xx_cds_common.c
@@ -379,14 +379,13 @@ mpc85xx_cds_pcibios_fixup(void)
                                         PCI_DEVICE_ID_VIA_82C586_2, NULL))) {
                 dev->irq = 10;
                 pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 10);
-		pci_dev_put(dev);
-        }
 
-	if ((dev = pci_get_device(PCI_VENDOR_ID_VIA,
+		if ((dev = pci_get_device(PCI_VENDOR_ID_VIA,
                                         PCI_DEVICE_ID_VIA_82C586_2, dev))) {
-                dev->irq = 11;
-                pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 11);
-		pci_dev_put(dev);
+	                dev->irq = 11;
+	                pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 11);
+			pci_dev_put(dev);
+		}
         }
 }
 #endif /* CONFIG_PCI */

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