[Qemu-devel] [PATCHv8 1/3] fw_cfg: switch fw_cfg_find() to locate the fw_cfg device by type rather than path

[Mark Cave-Ayland]

This will enable the fw_cfg device to be placed anywhere within the QOM tree
regardless of its machine location.

Note that we also add a comment to document the behaviour that we return NULL to
indicate failure where either no fw_cfg device or multiple fw_cfg devices are
found.

Signed-off-by: Mark Cave-Ayland <address@hidden>
---
 hw/nvram/fw_cfg.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 99bdbc2..8ef889a 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1017,7 +1017,12 @@ FWCfgState *fw_cfg_init_mem(hwaddr ctl_addr, hwaddr 
data_addr)
 
 FWCfgState *fw_cfg_find(void)
 {
-    return FW_CFG(object_resolve_path(FW_CFG_PATH, NULL));
+    /* Returns FWCfgState if only one fw_cfg device type exists. If zero or
+       more than one fw_cfg device are found then NULL is returned as per the
+       object_resolve_path_type() documentation. This behaviour is correct as
+       it ensures that we detect both missing fw_cfg devices and multiple
+       fw_cfg devices which could result in unpredictable behaviour. */
+    return FW_CFG(object_resolve_path_type("", TYPE_FW_CFG, NULL));
 }
 
 static void fw_cfg_class_init(ObjectClass *klass, void *data)
-- 
1.7.10.4