staging: comedi: comedidev.h: introduce comedi_to_pci_dev() helper

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.

---
v2: Ian Abbott pointed out that the dev->hw_dev needs to be checked
that it's non-NULL before passing it to to_pci_dev(). As Dan Carpenter pointed out, the container_of() just does pointer math with the offset. If you give it a NULL pointer it returns a bogus pointer back.

 drivers/staging/comedi/comedidev.h | 5 +++++
 1 file changed, 5 insertions(+)

index de8c99c..f713783 100644
@@ -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 dev->hw_dev ? to_pci_dev(dev->hw_dev) : NULL;
+}
+
 int comedi_buf_put(struct comedi_async *async, short x);
 int comedi_buf_get(struct comedi_async *async, short *x);
 

1.7.11