RE: [PATCH 01/90] staging: comedi: comedidev.h: introducecomedi_to_pci_dev() helper

From: H Hartley Sweeten
Date: Thu Jul 19 2012 - 13:27:46 EST

On Thursday, July 19, 2012 9:32 AM, Dan Carpenter wrote:
> On Thu, Jul 19, 2012 at 11:20:52AM -0500, H Hartley Sweeten wrote:
>> On Thursday, July 19, 2012 2:23 AM, Ian Abbott wrote:
>>> That needs to be something like:
>>> return dev->hw_dev ? to_pci_dev(dev->hw_dev) : NULL;
>> Hmm.. I'm not really sure.
>> I assumed that the container_of() macro would return NULL if the ptr passed to
>> it was NULL. But, I'm not sure how this actually unwinds for that case.
>> Greg, do you know if the NULL check is needed? It's is possible that the dev->hw_dev
>> pointer could be NULL.
> container_of() just does pointer math with the offset. Since
> ->hw_dev is not the first member of the pci_dev struct then
> to_pci_dev() never returns NULL. If you give it a NULL pointer it
> returns a bogus pointer back.

Thanks for the information.

I'll update PATCH 01/90 and repost it as v2.


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