s390/pci: rename get_zdev_by_bus() to zdev_from_bus()

Getting a zpci_dev via get_zdev_by_bus() uses the long lived reference
held in zbus->function[devfn]. This is accounted for in
pcibios_add_device() and pcibios_release_device().

Therefore there is no need to increment the reference count in
get_zdev_by_bus() as is done for get_zdev_by_fid(). Instead callers must
not access the device after pcibios_release_device() was called which is
necessary for common PCI code anyway. With this though the very similar
naming may be misleading so rename get_zdev_by_bus() to zdev_from_bus()
emphasizing that we are directly referencing the zdev via the bus.
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/pci/pci.c

@@ -400,7 +400,7 @@ EXPORT_SYMBOL(pci_iounmap);
 static int pci_read(struct pci_bus *bus, unsigned int devfn, int where,
 		    int size, u32 *val)
 {
-	struct zpci_dev *zdev = get_zdev_by_bus(bus, devfn);
+	struct zpci_dev *zdev = zdev_from_bus(bus, devfn);
 
 	return (zdev) ? zpci_cfg_load(zdev, where, val, size) : -ENODEV;
 }
@@ -408,7 +408,7 @@ static int pci_read(struct pci_bus *bus, unsigned int devfn, int where,
 static int pci_write(struct pci_bus *bus, unsigned int devfn, int where,
 		     int size, u32 val)
 {
-	struct zpci_dev *zdev = get_zdev_by_bus(bus, devfn);
+	struct zpci_dev *zdev = zdev_from_bus(bus, devfn);
 
 	return (zdev) ? zpci_cfg_store(zdev, where, val, size) : -ENODEV;
 }

arch/s390/pci/pci_bus.h

@@ -33,8 +33,8 @@ void zpci_free_domain(int domain);
 int zpci_setup_bus_resources(struct zpci_dev *zdev,
 			     struct list_head *resources);
 
-static inline struct zpci_dev *get_zdev_by_bus(struct pci_bus *bus,
-					       unsigned int devfn)
+static inline struct zpci_dev *zdev_from_bus(struct pci_bus *bus,
+					     unsigned int devfn)
 {
 	struct zpci_bus *zbus = bus->sysdata;