[v7,3/8] trace: Provide a generic tracing event descriptor

diff --git a/Makefile b/Makefile
index f659477..533d551 100644
--- a/Makefile
+++ b/Makefile
@@ -35,6 +35,9 @@  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 += trace/generated-events.h
+GENERATED_SOURCES += trace/generated-events.c
+
 GENERATED_HEADERS += trace/generated-tracers.h
 ifeq ($(TRACE_BACKEND),dtrace)
 GENERATED_HEADERS += trace/generated-tracers-dtrace.h
diff --git a/scripts/tracetool/backend/events.py b/scripts/tracetool/backend/events.py
new file mode 100644
index 0000000..5afce3e
--- /dev/null
+++ b/scripts/tracetool/backend/events.py
@@ -0,0 +1,23 @@ 
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Generic event description.
+
+This is a dummy backend to establish appropriate frontend/backend compatibility
+checks.
+"""
+
+__author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@linux.vnet.ibm.com"
+
+
+def events_h(events):
+    pass
+
+def events_c(events):
+    pass
diff --git a/scripts/tracetool/format/events_c.py b/scripts/tracetool/format/events_c.py
new file mode 100644
index 0000000..d670ec8
--- /dev/null
+++ b/scripts/tracetool/format/events_c.py
@@ -0,0 +1,39 @@ 
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Generate .c for event description.
+"""
+
+__author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@linux.vnet.ibm.com"
+
+
+from tracetool import out
+
+
+def begin(events):
+    out('/* This file is autogenerated by tracetool, do not edit. */',
+        '',
+        '#include "trace.h"',
+        '#include "trace/generated-events.h"',
+        '#include "trace/control.h"',
+        '',
+        )
+
+    out('TraceEvent trace_events[TRACE_EVENT_COUNT] = {')
+
+    for e in events:
+        out('    { .id = %(id)s, .name = \"%(name)s\", .sstate = %(sstate)s, .dstate = 0 },',
+            id = "TRACE_" + e.name.upper(),
+            name = e.name,
+            sstate = "TRACE_%s_ENABLED" % e.name.upper(),
+            )
+
+    out('};',
+        '',
+        )
diff --git a/scripts/tracetool/format/events_h.py b/scripts/tracetool/format/events_h.py
new file mode 100644
index 0000000..d30ccea
--- /dev/null
+++ b/scripts/tracetool/format/events_h.py
@@ -0,0 +1,50 @@ 
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Generate .h for event description.
+"""
+
+__author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@linux.vnet.ibm.com"
+
+
+from tracetool import out
+
+
+def begin(events):
+    out('/* This file is autogenerated by tracetool, do not edit. */',
+        '',
+        '#ifndef TRACE__GENERATED_EVENTS_H',
+        '#define TRACE__GENERATED_EVENTS_H',
+        '',
+        '#include <stdbool.h>',
+        ''
+        )
+
+    # event identifiers
+    out('typedef enum {')
+
+    for e in events:
+        out('    TRACE_%s,' % e.name.upper())
+
+    out('    TRACE_EVENT_COUNT',
+        '} TraceEventID;',
+        )
+
+    # static state
+    for e in events:
+        if 'disable' in e.properties:
+            enabled = 0
+        else:
+            enabled = 1
+        out('#define TRACE_%s_ENABLED %d' % (e.name.upper(), enabled))
+
+    out('#include "trace/event-internal.h"',
+        '',
+        '#endif  /* TRACE__GENERATED_EVENTS_H */',
+        )
diff --git a/scripts/tracetool/format/h.py b/scripts/tracetool/format/h.py
index 9a58de1..93132fc 100644
--- a/scripts/tracetool/format/h.py
+++ b/scripts/tracetool/format/h.py
@@ -25,14 +25,7 @@  def begin(events):
         '#include "qemu-common.h"')
 
 def end(events):
-    for e in events:
-        if "disable" in e.properties:
-            enabled = 0
-        else:
-            enabled = 1
-        out('#define TRACE_%s_ENABLED %d' % (e.name.upper(), enabled))
-    out('',
-        '#endif /* TRACE__GENERATED_TRACERS_H */')
+    out('#endif /* TRACE__GENERATED_TRACERS_H */')
 
 def nop(events):
     for e in events:
diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index b791723..9617c02 100644
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -1,6 +1,28 @@ 
 # -*- mode: makefile -*-
 
 ######################################################################
+# Auto-generated event descriptions
+
+$(obj)/generated-events.h: $(obj)/generated-events.h-timestamp
+$(obj)/generated-events.h-timestamp: $(SRC_PATH)/trace-events
+	$(call quiet-command,$(TRACETOOL) \
+		--format=events-h \
+		--backend=events \
+		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
+	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
+
+$(obj)/generated-events.c: $(obj)/generated-events.c-timestamp
+$(obj)/generated-events.c-timestamp: $(SRC_PATH)/trace-events
+	$(call quiet-command,$(TRACETOOL) \
+		--format=events-c \
+		--backend=events \
+		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
+	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
+
+trace-obj-y += generated-events.o
+
+
+######################################################################
 # Auto-generated tracing routines
 
 ifeq ($(TRACE_BACKEND),dtrace)
diff --git a/trace/event-internal.h b/trace/event-internal.h
new file mode 100644
index 0000000..b2310d9
--- /dev/null
+++ b/trace/event-internal.h
@@ -0,0 +1,33 @@ 
+/*
+ * Interface for configuring and controlling the state of tracing events.
+ *
+ * Copyright (C) 2012 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef TRACE__EVENT_INTERNAL_H
+#define TRACE__EVENT_INTERNAL_H
+
+#include "trace/generated-events.h"
+
+
+/**
+ * TraceEvent:
+ * @id: Unique event identifier.
+ * @name: Event name.
+ * @sstate: Static tracing state.
+ * @dstate: Dynamic tracing state.
+ *
+ * Opaque generic description of a tracing event.
+ */
+typedef struct TraceEvent {
+    TraceEventID id;
+    const char * name;
+    const bool sstate;
+    bool dstate;
+} TraceEvent;
+
+
+#endif  /* TRACE__EVENT_INTERNAL_H */