[PATCH] Driver Core: Make dev_info and friends print the bus name if there is no driver

This patch (as721) makes dev_info and related macros print the device's
bus name if the device doesn't have a driver, instead of printing just a
blank. If the device isn't on a bus either... well, then it does leave
a blank space. But it will be easier for someone else to change if they
want.

Cc: Matthew Wilcox <[e-mail]>
Signed-off-by: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/core.c

···
  * sysfs bindings for devices.
  */
 
+/**
+ * dev_driver_string - Return a device's driver name, if at all possible
+ * @dev: struct device to get the name of
+ *
+ * Will return the device's driver's name if it is bound to a device.  If
+ * the device is not bound to a device, it will return the name of the bus
+ * it is attached to.  If it is not attached to a bus either, an empty
+ * string will be returned.
+ */
+const char *dev_driver_string(struct device *dev)
+{
+	return dev->driver ? dev->driver->name :
+			(dev->bus ? dev->bus->name : "");
+}
+EXPORT_SYMBOL_GPL(dev_driver_string);
+
 #define to_dev(obj) container_of(obj, struct device, kobj)
 #define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
 

include/linux/device.h

···
 extern void firmware_unregister(struct subsystem *);
 
 /* debugging and troubleshooting/diagnostic helpers. */
+extern const char *dev_driver_string(struct device *dev);
 #define dev_printk(level, dev, format, arg...)	\
-	printk(level "%s %s: " format , (dev)->driver ? (dev)->driver->name : "" , (dev)->bus_id , ## arg)
+	printk(level "%s %s: " format , dev_driver_string(dev) , (dev)->bus_id , ## arg)
 
 #ifdef DEBUG
 #define dev_dbg(dev, format, arg...)		\