greybus: connection: add offloaded connection flag

Add an offloaded connection flag, which is used to mark a connection as
offloaded and prevent drivers from initiating operation over it.

This will be used for the audio and camera data connections.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.h

@@ -15,6 +15,7 @@
 
 #define GB_CONNECTION_FLAG_CSD		BIT(0)
 #define GB_CONNECTION_FLAG_NO_FLOWCTRL	BIT(1)
+#define GB_CONNECTION_FLAG_OFFLOADED	BIT(2)
 
 enum gb_connection_state {
 	GB_CONNECTION_STATE_INVALID	= 0,
@@ -95,6 +96,11 @@ gb_connection_flow_control_disabled(struct gb_connection *connection)
 	return connection->flags & GB_CONNECTION_FLAG_NO_FLOWCTRL;
 }
 
+static inline bool gb_connection_is_offloaded(struct gb_connection *connection)
+{
+	return connection->flags & GB_CONNECTION_FLAG_OFFLOADED;
+}
+
 static inline void *gb_connection_get_data(struct gb_connection *connection)
 {
 	return connection->private;

drivers/staging/greybus/operation.c

@@ -654,6 +654,9 @@ int gb_operation_request_send(struct gb_operation *operation,
 	unsigned int cycle;
 	int ret;
 
+	if (gb_connection_is_offloaded(connection))
+		return -EBUSY;
+
 	if (!callback)
 		return -EINVAL;
 
@@ -950,8 +953,9 @@ void gb_connection_recv(struct gb_connection *connection,
 	size_t msg_size;
 	u16 operation_id;
 
-	if (connection->state != GB_CONNECTION_STATE_ENABLED &&
-		connection->state != GB_CONNECTION_STATE_ENABLED_TX) {
+	if ((connection->state != GB_CONNECTION_STATE_ENABLED &&
+			connection->state != GB_CONNECTION_STATE_ENABLED_TX) ||
+			gb_connection_is_offloaded(connection)) {
 		dev_warn(dev, "%s: dropping %zu received bytes\n",
 				connection->name, size);
 		return;