greybus: loopback: make loopback type input equivalent to protocol type

Sepcifying loopback operation type with a type value that is internal to
the loopback driver is non-intunitive and requires reading code to
understand. Remove confusing duplicate definitions and update code to
accept the greybus-specification function identity defintiions as the
appropriate type values for initiating loopback operations.

See greybus-spec section 10.16.1 'Greybus Loopback Message Types' for a
full list of valid messages to set this type field to.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/loopback.c

@@ -45,12 +45,6 @@ struct gb_loopback {
 	u32 error;
 };
 
-/* Current function (type of traffic generated by the loopback thread) */
-#define GB_LOOPBACK_FN_NONE				0x00
-#define GB_LOOPBACK_FN_PING				0x01
-#define GB_LOOPBACK_FN_XFER				0x02
-#define GB_LOOPBACK_FN_COUNT				0x03
-
 #define GB_LOOPBACK_MS_WAIT_MAX				1000
 #define GB_LOOPBACK_SIZE_MAX				SZ_4K
 
@@ -117,10 +111,16 @@ static DEVICE_ATTR_RW(field)
 static void gb_loopback_reset_stats(struct gb_loopback *gb);
 static void gb_loopback_check_attr(struct gb_loopback *gb)
 {
+	switch (gb->type) {
+	case GB_LOOPBACK_TYPE_PING:
+	case GB_LOOPBACK_TYPE_TRANSFER:
+		break;
+	default:
+		gb->type = 0;
+		break;
+	}
 	if (gb->ms_wait > GB_LOOPBACK_MS_WAIT_MAX)
 		gb->ms_wait = GB_LOOPBACK_MS_WAIT_MAX;
-	if (gb->type >= GB_LOOPBACK_FN_COUNT)
-		gb->type = GB_LOOPBACK_FN_NONE;
 	if (gb->size > GB_LOOPBACK_SIZE_MAX)
 		gb->size = GB_LOOPBACK_SIZE_MAX;
 	gb->error = 0;
@@ -337,13 +337,13 @@ static int gb_loopback_fn(void *data)
 	struct gb_loopback *gb = (struct gb_loopback *)data;
 
 	while (!kthread_should_stop()) {
-		if (gb->type == GB_LOOPBACK_FN_NONE) {
+		if (!gb->type) {
 			msleep(1000);
 			continue;
 		}
-		if (gb->type == GB_LOOPBACK_FN_PING)
+		if (gb->type == GB_LOOPBACK_TYPE_PING)
 			error = gb_loopback_ping(gb, &tlat);
-		else if (gb->type == GB_LOOPBACK_FN_XFER)
+		else if (gb->type == GB_LOOPBACK_TYPE_TRANSFER)
 			error = gb_loopback_transfer(gb, &tlat, gb->size);
 		if (error)
 			gb->error++;