hw/arm/sysbus-fdt: Only call match_fn callback if the type matches

Commit af7d64ede0b9 (hw/arm/sysbus-fdt: Allow device matching with DT
compatible value) introduced a match_fn callback which gets called
for each registered combo to check whether a sysbus device can be
dynamically instantiated. However the callback gets called even if
the device type does not match the binding combo typename field.
This causes an assert when passing "-device ramfb" to the qemu
command line as vfio_platform_match() gets called on a non
vfio-platform device.

To fix this regression, let's change the add_fdt_node() logic so
that we first check the type and if the match_fn callback is defined,
then we also call it.

Binding combos only requesting a type check do not define the
match_fn callback.

Fixes: af7d64ede0b9 (hw/arm/sysbus-fdt: Allow device matching with
DT compatible value)

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Message-id: 20181106184212.29377-1-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/sysbus-fdt.c

@@ -449,7 +449,7 @@ static bool type_match(SysBusDevice *sbdev, const BindingEntry *entry)
     return !strcmp(object_get_typename(OBJECT(sbdev)), entry->typename);
 }
 
-#define TYPE_BINDING(type, add_fn) {(type), NULL, (add_fn), type_match}
+#define TYPE_BINDING(type, add_fn) {(type), NULL, (add_fn), NULL}
 
 /* list of supported dynamic sysbus bindings */
 static const BindingEntry bindings[] = {
@@ -481,10 +481,12 @@ static void add_fdt_node(SysBusDevice *sbdev, void *opaque)
     for (i = 0; i < ARRAY_SIZE(bindings); i++) {
         const BindingEntry *iter = &bindings[i];
 
-        if (iter->match_fn(sbdev, iter)) {
-            ret = iter->add_fn(sbdev, opaque);
-            assert(!ret);
-            return;
+        if (type_match(sbdev, iter)) {
+            if (!iter->match_fn || iter->match_fn(sbdev, iter)) {
+                ret = iter->add_fn(sbdev, opaque);
+                assert(!ret);
+                return;
+            }
         }
     }
     error_report("Device %s can not be dynamically instantiated",