i2c:smbus_slave: Add an SMBus vmstate structure

There is no vmstate handling for SMBus, so no device sitting on SMBus
can have a state transfer that works reliably.  So add it.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

hw/i2c/smbus_slave.c

@@ -201,6 +201,24 @@ static void smbus_device_class_init(ObjectClass *klass, void *data)
     sc->send = smbus_i2c_send;
 }
 
+bool smbus_vmstate_needed(SMBusDevice *dev)
+{
+    return dev->mode != SMBUS_IDLE;
+}
+
+const VMStateDescription vmstate_smbus_device = {
+    .name = TYPE_SMBUS_DEVICE,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields      = (VMStateField[]) {
+        VMSTATE_I2C_SLAVE(i2c, SMBusDevice),
+        VMSTATE_INT32(mode, SMBusDevice),
+        VMSTATE_INT32(data_len, SMBusDevice),
+        VMSTATE_UINT8_ARRAY(data_buf, SMBusDevice, SMBUS_DATA_MAX_LEN),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const TypeInfo smbus_device_type_info = {
     .name = TYPE_SMBUS_DEVICE,
     .parent = TYPE_I2C_SLAVE,

include/hw/i2c/smbus_slave.h

@@ -69,14 +69,32 @@ typedef struct SMBusDeviceClass
     uint8_t (*receive_byte)(SMBusDevice *dev);
 } SMBusDeviceClass;
 
+#define SMBUS_DATA_MAX_LEN 34  /* command + len + 32 bytes of data.  */
+
 struct SMBusDevice {
     /* The SMBus protocol is implemented on top of I2C.  */
     I2CSlave i2c;
 
     /* Remaining fields for internal use only.  */
-    int mode;
-    int data_len;
-    uint8_t data_buf[34]; /* command + len + 32 bytes of data.  */
+    int32_t mode;
+    int32_t data_len;
+    uint8_t data_buf[SMBUS_DATA_MAX_LEN];
 };
 
+extern const VMStateDescription vmstate_smbus_device;
+
+#define VMSTATE_SMBUS_DEVICE(_field, _state) {                       \
+    .name       = (stringify(_field)),                               \
+    .size       = sizeof(SMBusDevice),                               \
+    .vmsd       = &vmstate_smbus_device,                             \
+    .flags      = VMS_STRUCT,                                        \
+    .offset     = vmstate_offset_value(_state, _field, SMBusDevice), \
+}
+
+/*
+ * Users should call this in their .needed functions to know if the
+ * SMBus slave data needs to be transferred.
+ */
+bool smbus_vmstate_needed(SMBusDevice *dev);
+
 #endif