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>

Makefile

@@ -45,8 +45,8 @@ endif
 endif
 
 GENERATED_HEADERS = config-host.h qemu-options.def
-GENERATED_HEADERS += qmp-commands.h qapi-types.h qapi-visit.h
-GENERATED_SOURCES += qmp-marshal.c qapi-types.c qapi-visit.c
+GENERATED_HEADERS += qmp-commands.h qapi-types.h qapi-visit.h qapi-event.h
+GENERATED_SOURCES += qmp-marshal.c qapi-types.c qapi-visit.c qapi-event.c
 
 GENERATED_HEADERS += trace/generated-events.h
 GENERATED_SOURCES += trace/generated-events.c
@@ -202,7 +202,7 @@ Makefile: $(version-obj-y) $(version-lobj-y)
 # Build libraries
 
 libqemustub.a: $(stub-obj-y)
-libqemuutil.a: $(util-obj-y) qapi-types.o qapi-visit.o
+libqemuutil.a: $(util-obj-y) qapi-types.o qapi-visit.o qapi-event.o
 
 block-modules = $(foreach o,$(block-obj-m),"$(basename $(subst /,-,$o))",) NULL
 util/module.o-cflags = -D'CONFIG_BLOCK_MODULES=$(block-modules)'
@@ -259,6 +259,11 @@ $(qapi-modules) $(SRC_PATH)/scripts/qapi-visit.py $(qapi-py)
 	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py \
 		$(gen-out-type) -o "." -b -i $<, \
 		"  GEN   $@")
+qapi-event.c qapi-event.h :\
+$(qapi-modules) $(SRC_PATH)/scripts/qapi-event.py $(qapi-py)
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-event.py \
+		$(gen-out-type) -o "." -b -i $<, \
+		"  GEN   $@")
 qmp-commands.h qmp-marshal.c :\
 $(qapi-modules) $(SRC_PATH)/scripts/qapi-commands.py $(qapi-py)
 	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py \

Makefile.objs

@@ -12,7 +12,7 @@ block-obj-y += main-loop.o iohandler.o qemu-timer.o
 block-obj-$(CONFIG_POSIX) += aio-posix.o
 block-obj-$(CONFIG_WIN32) += aio-win32.o
 block-obj-y += block/
-block-obj-y += qapi-types.o qapi-visit.o
+block-obj-y += qapi-types.o qapi-visit.o qapi-event.o
 block-obj-y += qemu-io-cmds.o
 
 block-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o

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 ==