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stream: Add flow control API

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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>
This commit is contained in:
Peter Crosthwaite 2013-04-16 10:27:16 +10:00 • committed by Edgar E. Iglesias
parent 210914e299
commit 35e60bfdbc
4 changed files with 48 additions and 9 deletions
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33
include/hw/stream.h
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@ -18,14 +18,41 @@ typedef struct StreamSlave {
Object Parent;
} StreamSlave;
typedef void (*StreamCanPushNotifyFn)(void *opaque);
typedef struct StreamSlaveClass {
InterfaceClass parent;
void (*push)(StreamSlave *obj, unsigned char *buf, size_t len,
/**
* can push - determine if a stream slave is capable of accepting at least
* one byte of data. Returns false if cannot accept. If not implemented, the
* slave is assumed to always be capable of recieveing.
* @notify: Optional callback that the slave will call when the slave is
* capable of recieving again. Only called if false is returned.
* @notify_opaque: opaque data to pass to notify call.
*/
bool (*can_push)(StreamSlave *obj, StreamCanPushNotifyFn notify,
void *notify_opaque);
/**
* push - push data to a Stream slave. The number of bytes pushed is
* returned. If the slave short returns, the master must wait before trying
* again, the slave may continue to just return 0 waiting for the vm time to
* advance. The can_push() function can be used to trap the point in time
* where the slave is ready to recieve again, otherwise polling on a QEMU
* timer will work.
* @obj: Stream slave to push to
* @buf: Data to write
* @len: Maximum number of bytes to write
*/
size_t (*push)(StreamSlave *obj, unsigned char *buf, size_t len,
uint32_t *app);
} StreamSlaveClass;
void
size_t
stream_push(StreamSlave *sink, uint8_t *buf, size_t len, uint32_t *app);
bool
stream_can_push(StreamSlave *sink, StreamCanPushNotifyFn notify,
void *notify_opaque);
#endif /* STREAM_H */