stream: Add flow control API

Add basic flow control to stream. A stream slave may return short, indicating
that it is not capable of accepting any more data at the present time. Polling
or a callback can be used via the can_push() function to determine when the
slave can receive again.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/hw/core/stream.c b/hw/core/stream.c
index a07d6a56d3..5397a8d74a 100644
--- a/hw/core/stream.c
+++ b/hw/core/stream.c
@@ -1,11 +1,20 @@
 #include "hw/stream.h"
 
-void
+size_t
 stream_push(StreamSlave *sink, uint8_t *buf, size_t len, uint32_t *app)
 {
     StreamSlaveClass *k =  STREAM_SLAVE_GET_CLASS(sink);
 
-    k->push(sink, buf, len, app);
+    return k->push(sink, buf, len, app);
+}
+
+bool
+stream_can_push(StreamSlave *sink, StreamCanPushNotifyFn notify,
+                void *notify_opaque)
+{
+    StreamSlaveClass *k =  STREAM_SLAVE_GET_CLASS(sink);
+
+    return k->can_push ? k->can_push(sink, notify, notify_opaque) : true;
 }
 
 static const TypeInfo stream_slave_info = {