w1: add fast search for single slave bus

This enables a much more efficient way of device searching. It uses the
1-wire read-rom operation which allows the direct reading of the slave
address. BUT this works only with exactly one slave on the bus.

Signed-off-by: Hubert Feurstein <[e-mail]>
Acked-by: Evgeniy Polyakov <[e-mail]>

index c374978..9761950 100644
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/w1/w1.c

···
 			break;
 		}
 
+		/* Do fast search on single slave bus */
+		if (dev->max_slave_count == 1) {
+			w1_write_8(dev, W1_READ_ROM);
+
+			if (w1_read_block(dev, (u8 *)&rn, 8) == 8 && rn)
+				cb(dev, rn);
+
+			break;
+		}
+
 		/* Start the search */
 		w1_write_8(dev, search_type);
 		for (i = 0; i < 64; ++i) {