Re: [KJ] question about pci_dev_put

[Mark Hollomon <markhollomon@comcast.net>]

Nishanth Aravamudan wrote:
> On 18.05.2006 [01:16:22 +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 ?
> 
> /me knows nothing about the PCI space, but looking at the comments for
> pci_get_device() and tracing what pci_dev_put() does, it seems like you
> are right.
> 
> It seems like the correct method is to remove the pci_dev_put(dev); from
> the first if above and change the second one to
> 
> 	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);
> 	} else
> 		pci_dev_put(dev);

That can't be right. you will only reach the else leg if pci_get_device() returns
NULL. which means that you will be calling pci_dev_put(NULL).

-- 
Mark Hollomon
_______________________________________________
Kernel-janitors mailing list
Kernel-janitors@lists.osdl.org
https://lists.osdl.org/mailman/listinfo/kernel-janitors