USB: nop-usb-xceiv: behave when linked as a module

The NOP OTG transceiver driver needs to be usable from modules.
Make sure its symbols are always accessible at both compile and
link time, and make sure the device instance is allocated from
the heap so that device lifetime rules are obeyed.

Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/otg/nop-usb-xceiv.c

···
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  *
  * Current status:
- * 	this is to add "nop" transceiver for all those phy which is
- * 	autonomous such as isp1504 etc.
+ *	This provides a "nop" transceiver for PHYs which are
+ *	autonomous such as isp1504, isp1707, etc.
  */
 
 #include <linux/module.h>
···
 	struct device		*dev;
 };
 
-static u64 nop_xceiv_dmamask = DMA_BIT_MASK(32);
-
-static struct platform_device nop_xceiv_device = {
-	.name           = "nop_usb_xceiv",
-	.id             = -1,
-	.dev = {
-		.dma_mask               = &nop_xceiv_dmamask,
-		.coherent_dma_mask      = DMA_BIT_MASK(32),
-		.platform_data          = NULL,
-	},
-};
+static struct platform_device *pd;
 
 void usb_nop_xceiv_register(void)
 {
-	if (platform_device_register(&nop_xceiv_device) < 0) {
+	if (pd)
+		return;
+	pd = platform_device_register_simple("nop_usb_xceiv", -1, NULL, 0);
+	if (!pd) {
 		printk(KERN_ERR "Unable to register usb nop transceiver\n");
 		return;
 	}
 }
+EXPORT_SYMBOL(usb_nop_xceiv_register);
 
 void usb_nop_xceiv_unregister(void)
 {
-	platform_device_unregister(&nop_xceiv_device);
+	platform_device_unregister(pd);
 }
+EXPORT_SYMBOL(usb_nop_xceiv_unregister);
 
 static inline struct nop_usb_xceiv *xceiv_to_nop(struct otg_transceiver *x)
 {

include/linux/usb/otg.h

···
 
 /* for board-specific init logic */
 extern int otg_set_transceiver(struct otg_transceiver *);
-#ifdef CONFIG_NOP_USB_XCEIV
+
+/* sometimes transceivers are accessed only through e.g. ULPI */
 extern void usb_nop_xceiv_register(void);
 extern void usb_nop_xceiv_unregister(void);
-#endif
 
 
 /* for usb host and peripheral controller drivers */