greybus: loopback: add sink to loopback protocol

Loopback sink command will operate as an amalgam of the ping and tranfer
operations. Sink will send an ACK'd variable size operation over greybus.
Unlike the transfer type which transmits the received data back, the sink
type will simply ACK without sending the received data back.

This patch adds the kernel side of the sink command.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/greybus_protocols.h

@@ -668,6 +668,7 @@ struct gb_uart_serial_state_request {
 #define	GB_LOOPBACK_TYPE_PROTOCOL_VERSION	0x01
 #define	GB_LOOPBACK_TYPE_PING			0x02
 #define	GB_LOOPBACK_TYPE_TRANSFER		0x03
+#define GB_LOOPBACK_TYPE_SINK			0x04
 
 struct gb_loopback_transfer_request {
 	__le32	len;

drivers/staging/greybus/loopback.c

@@ -114,6 +114,7 @@ static void gb_loopback_check_attr(struct gb_loopback *gb)
 	switch (gb->type) {
 	case GB_LOOPBACK_TYPE_PING:
 	case GB_LOOPBACK_TYPE_TRANSFER:
+	case GB_LOOPBACK_TYPE_SINK:
 		break;
 	default:
 		gb->type = 0;
@@ -164,6 +165,31 @@ static struct attribute *loopback_attrs[] = {
 };
 ATTRIBUTE_GROUPS(loopback);
 
+static int gb_loopback_sink(struct gb_loopback *gb,
+				struct timeval *tping, u32 len)
+{
+	struct timeval ts, te;
+	u64 elapsed_nsecs;
+	struct gb_loopback_transfer_request *request;
+	int retval;
+
+	request = kmalloc(len + sizeof(*request), GFP_KERNEL);
+	if (!request)
+		return -ENOMEM;
+
+	request->len = cpu_to_le32(len);
+
+	do_gettimeofday(&ts);
+	retval = gb_operation_sync(gb->connection, GB_LOOPBACK_TYPE_SINK,
+				   request, len + sizeof(*request), NULL, 0);
+	do_gettimeofday(&te);
+	elapsed_nsecs = timeval_to_ns(&te) - timeval_to_ns(&ts);
+	*tping = ns_to_timeval(elapsed_nsecs);
+
+	kfree(request);
+	return retval;
+}
+
 static int gb_loopback_transfer(struct gb_loopback *gb,
 				struct timeval *tping, u32 len)
 {
@@ -235,6 +261,7 @@ static int gb_loopback_request_recv(u8 type, struct gb_operation *operation)
 			"module-initiated version operation\n");
 		return -EINVAL;
 	case GB_LOOPBACK_TYPE_PING:
+	case GB_LOOPBACK_TYPE_SINK:
 		return 0;
 	case GB_LOOPBACK_TYPE_TRANSFER:
 		if (operation->request->payload_size < sizeof(*request)) {
@@ -345,6 +372,8 @@ static int gb_loopback_fn(void *data)
 			error = gb_loopback_ping(gb, &tlat);
 		else if (gb->type == GB_LOOPBACK_TYPE_TRANSFER)
 			error = gb_loopback_transfer(gb, &tlat, gb->size);
+		else if (gb->type == GB_LOOPBACK_TYPE_SINK)
+			error = gb_loopback_sink(gb, &tlat, gb->size);
 		if (error)
 			gb->error++;
 		if (gb->ts.tv_usec == 0 && gb->ts.tv_sec == 0) {