qdev: Display warning about unused -global

This can help a user understand why -global was ignored.

For example: with "-vga cirrus"; "-global vga.vgamem_mb=16" is just
ignored when "-global cirrus-vga.vgamem_mb=16" is not.

This is currently clear when the wrong property is provided:

out/x86_64-softmmu/qemu-system-x86_64 -global cirrus-vga.vram_size_mb=16 -monitor pty -vga cirrus
char device redirected to /dev/pts/20 (label compat_monitor0)
qemu-system-x86_64: Property '.vram_size_mb' not found
Aborted (core dumped)

vs

out/x86_64-softmmu/qemu-system-x86_64 -global vga.vram_size_mb=16 -monitor pty -vga cirrus
char device redirected to /dev/pts/20 (label compat_monitor0)
VNC server running on `::1:5900'
^Cqemu: terminating on signal 2

Signed-off-by: Don Slutz <dslutz@verizon.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index dbe473c..bbed829 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -231,10 +231,18 @@ struct PropertyInfo {
     ObjectPropertyRelease *release;
 };
 
+/**
+ * GlobalProperty:
+ * @not_used: Track use of a global property.  Defaults to false in all C99
+ * struct initializations.
+ *
+ * This prevents reports of .compat_props when they are not used.
+ */
 typedef struct GlobalProperty {
     const char *driver;
     const char *property;
     const char *value;
+    bool not_used;
     QTAILQ_ENTRY(GlobalProperty) next;
 } GlobalProperty;