strange prink_debug output with dev_path

[YhLu]

What is the difference between 
        printk_debug("smbus:  %s[%d]->",  dev_path(dev->bus->dev),
dev->bus->link );
        printk_debug("%s",  dev_path(dev));

and 

        printk_debug("smbus:  %s[%d]->%s",  dev_path(dev->bus->dev),
dev->bus->link ,  dev_path(dev));

the first print 
smbus:  PCI: 01:01.1[0]->I2C: 50

the second one print
smbus:  PCI: 01:01.1[0]-> PCI: 01:01.1

YH