qapi script: add event support

qapi-event.py will parse the schema and generate qapi-event.c, then
the API in qapi-event.c can be used to handle events in qemu code.
All API have prefix "qapi_event".

The script mainly includes two parts: generate API for each event
define, generate an enum type for all defined events.

Since in some cases the real emit behavior may change, for example,
qemu-img would not send a event, a callback layer is used to
control the behavior. As a result, the stubs at compile time
can be saved, the binding of block layer code and monitor code
will become looser.

Signed-off-by: Wenchao Xia <wenchaoqemu@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index dea0d505a7..3a0c99e1da 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -215,6 +215,24 @@ An example command is:
    'data': { 'arg1': 'str', '*arg2': 'str' },
    'returns': 'str' }
 
+=== Events ===
+
+Events are defined with the keyword 'event'.  When 'data' is also specified,
+additional info will be carried on.  Finally there will be C API generated
+in qapi-event.h; when called by QEMU code, a message with timestamp will
+be emitted on the wire.  If timestamp is -1, it means failure to retrieve host
+time.
+
+An example event is:
+
+{ 'event': 'EVENT_C',
+  'data': { '*a': 'int', 'b': 'str' } }
+
+Resulting in this JSON object:
+
+{ "event": "EVENT_C",
+  "data": { "b": "test string" },
+  "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }
 
 == Code generation ==