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: > > On 2012-07-19 02:24, H Hartley Sweeten wrote: > >> Introduce a wrapper for to_pci_dev() to allow the comedi pci drivers > >> to store the pci_dev pointer in the comedi_device hw_dev variable and > >> retrieve it easily. > >> > >> Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com> > >> Cc: Ian Abbott <abbo...@mev.co.uk> > >> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> > >> --- > >> drivers/staging/comedi/comedidev.h | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/drivers/staging/comedi/comedidev.h > >> b/drivers/staging/comedi/comedidev.h > >> index de8c99c..620222d 100644 > >> --- a/drivers/staging/comedi/comedidev.h > >> +++ b/drivers/staging/comedi/comedidev.h > >> @@ -446,6 +446,11 @@ static inline void comedi_set_hw_dev(struct > >> comedi_device *dev, > >> } > >> } > >> > >> +static inline struct pci_dev *comedi_to_pci_dev(struct comedi_device *dev) > >> +{ > >> + return to_pci_dev(dev->hw_dev); > >> +} > >> + > > > > 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. regards, dan carpenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/