diff --git a/hw/fw_cfg.c b/hw/fw_cfg.c
index b25afff..2e3662d 100644
--- a/hw/fw_cfg.c
+++ b/hw/fw_cfg.c
@@ -45,11 +45,11 @@ typedef struct _FWCfgEntry {
     FWCfgCallback callback;
 } FWCfgEntry;
 
-typedef struct _FWCfgState {
+struct _FWCfgState {
     FWCfgEntry entries[2][FW_CFG_MAX_ENTRY];
     uint16_t cur_entry;
     uint32_t cur_offset;
-} FWCfgState;
+};
 
 static void fw_cfg_write(FWCfgState *s, uint8_t value)
 {
@@ -210,9 +210,8 @@ static const VMStateDescription vmstate_fw_cfg = {
     }
 };
 
-int fw_cfg_add_bytes(void *opaque, uint16_t key, uint8_t *data, uint32_t len)
+int fw_cfg_add_bytes(FWCfgState *s, uint16_t key, uint8_t *data, uint32_t len)
 {
-    FWCfgState *s = opaque;
     int arch = !!(key & FW_CFG_ARCH_LOCAL);
 
     key &= FW_CFG_ENTRY_MASK;
@@ -226,37 +225,36 @@ int fw_cfg_add_bytes(void *opaque, uint16_t key, uint8_t *data, uint32_t len)
     return 1;
 }
 
-int fw_cfg_add_i16(void *opaque, uint16_t key, uint16_t value)
+int fw_cfg_add_i16(FWCfgState *s, uint16_t key, uint16_t value)
 {
     uint16_t *copy;
 
     copy = qemu_malloc(sizeof(value));
     *copy = cpu_to_le16(value);
-    return fw_cfg_add_bytes(opaque, key, (uint8_t *)copy, sizeof(value));
+    return fw_cfg_add_bytes(s, key, (uint8_t *)copy, sizeof(value));
 }
 
-int fw_cfg_add_i32(void *opaque, uint16_t key, uint32_t value)
+int fw_cfg_add_i32(FWCfgState *s, uint16_t key, uint32_t value)
 {
     uint32_t *copy;
 
     copy = qemu_malloc(sizeof(value));
     *copy = cpu_to_le32(value);
-    return fw_cfg_add_bytes(opaque, key, (uint8_t *)copy, sizeof(value));
+    return fw_cfg_add_bytes(s, key, (uint8_t *)copy, sizeof(value));
 }
 
-int fw_cfg_add_i64(void *opaque, uint16_t key, uint64_t value)
+int fw_cfg_add_i64(FWCfgState *s, uint16_t key, uint64_t value)
 {
     uint64_t *copy;
 
     copy = qemu_malloc(sizeof(value));
     *copy = cpu_to_le64(value);
-    return fw_cfg_add_bytes(opaque, key, (uint8_t *)copy, sizeof(value));
+    return fw_cfg_add_bytes(s, key, (uint8_t *)copy, sizeof(value));
 }
 
-int fw_cfg_add_callback(void *opaque, uint16_t key, FWCfgCallback callback,
+int fw_cfg_add_callback(FWCfgState *s, uint16_t key, FWCfgCallback callback,
                         void *callback_opaque, uint8_t *data, size_t len)
 {
-    FWCfgState *s = opaque;
     int arch = !!(key & FW_CFG_ARCH_LOCAL);
 
     if (!(key & FW_CFG_WRITE_CHANNEL))
@@ -275,8 +273,8 @@ int fw_cfg_add_callback(void *opaque, uint16_t key, FWCfgCallback callback,
     return 1;
 }
 
-void *fw_cfg_init(uint32_t ctl_port, uint32_t data_port,
-		target_phys_addr_t ctl_addr, target_phys_addr_t data_addr)
+FWCfgState *fw_cfg_init(uint32_t ctl_port, uint32_t data_port,
+                        target_phys_addr_t ctl_addr, target_phys_addr_t data_addr)
 {
     FWCfgState *s;
     int io_ctl_memory, io_data_memory;
diff --git a/hw/fw_cfg.h b/hw/fw_cfg.h
index 7070c94..b06665e 100644
--- a/hw/fw_cfg.h
+++ b/hw/fw_cfg.h
@@ -37,14 +37,16 @@
 #ifndef NO_QEMU_PROTOS
 typedef void (*FWCfgCallback)(void *opaque, uint8_t *data);
 
-int fw_cfg_add_bytes(void *opaque, uint16_t key, uint8_t *data, uint32_t len);
-int fw_cfg_add_i16(void *opaque, uint16_t key, uint16_t value);
-int fw_cfg_add_i32(void *opaque, uint16_t key, uint32_t value);
-int fw_cfg_add_i64(void *opaque, uint16_t key, uint64_t value);
-int fw_cfg_add_callback(void *opaque, uint16_t key, FWCfgCallback callback,
+typedef struct _FWCfgState FWCfgState;
+int fw_cfg_add_bytes(FWCfgState *s, uint16_t key, uint8_t *data, uint32_t len);
+int fw_cfg_add_i16(FWCfgState *s, uint16_t key, uint16_t value);
+int fw_cfg_add_i32(FWCfgState *s, uint16_t key, uint32_t value);
+int fw_cfg_add_i64(FWCfgState *s, uint16_t key, uint64_t value);
+int fw_cfg_add_callback(FWCfgState *s, uint16_t key, FWCfgCallback callback,
                         void *callback_opaque, uint8_t *data, size_t len);
-void *fw_cfg_init(uint32_t ctl_port, uint32_t data_port,
-		target_phys_addr_t crl_addr, target_phys_addr_t data_addr);
+int fw_cfg_add_file(FWCfgState *s, uint8_t type, uint8_t *data, uint32_t len);
+FWCfgState *fw_cfg_init(uint32_t ctl_port, uint32_t data_port,
+                        target_phys_addr_t crl_addr, target_phys_addr_t data_addr);
 
 #endif /* NO_QEMU_PROTOS */
 
