ptp: Add a method for obtaining the device index.

This commit adds a method that MAC drivers may call in order to find out
the device number of their associated PTP Hardware Clock.

Signed-off-by: Richard Cochran <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ptp/ptp_clock.c

···
 }
 EXPORT_SYMBOL(ptp_clock_event);
 
+int ptp_clock_index(struct ptp_clock *ptp)
+{
+	return ptp->index;
+}
+EXPORT_SYMBOL(ptp_clock_index);
+
 /* module operations */
 
 static void __exit ptp_exit(void)

include/linux/ptp_clock_kernel.h

···
 extern void ptp_clock_event(struct ptp_clock *ptp,
 			    struct ptp_clock_event *event);
 
+/**
+ * ptp_clock_index() - obtain the device index of a PTP clock
+ *
+ * @ptp:    The clock obtained from ptp_clock_register().
+ */
+
+extern int ptp_clock_index(struct ptp_clock *ptp);
+
 #endif