Re: [Qemu-devel] [PATCHv4 3/5] fw_cfg: move assert() and linking of fw_cfg device to the machine into instance_init()

[Laszlo Ersek]

On 06/16/17 15:23, Mark Cave-Ayland wrote:
> In preparation for calling fw_cfg_init1() during realize rather than during
> init, move the assert() checking for existing fw_cfg devices and the linking
> of the device to the machine with object_property_add_child() to a new
> fw_cfg instance_init() function.
> 
> This guarantees that we will still assert() correctly if more than one fw_cfg
> device is instantiated by accident.
> 
> Signed-off-by: Mark Cave-Ayland <address@hidden>
> ---
>  hw/nvram/fw_cfg.c |   14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index e217239..39fcc04 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -916,10 +916,6 @@ static void fw_cfg_init1(DeviceState *dev)
>      MachineState *machine = MACHINE(qdev_get_machine());
>      uint32_t version = FW_CFG_VERSION;
>  
> -    assert(!object_resolve_path(FW_CFG_PATH, NULL));
> -
> -    object_property_add_child(OBJECT(machine), FW_CFG_NAME, OBJECT(s), NULL);
> -
>      qdev_init_nofail(dev);
>  
>      fw_cfg_add_bytes(s, FW_CFG_SIGNATURE, (char *)"QEMU", 4);
> @@ -1021,6 +1017,15 @@ FWCfgState *fw_cfg_find(void)
>      return FW_CFG(object_resolve_path(FW_CFG_PATH, NULL));
>  }
>  
> +static void fw_cfg_init(Object *obj)
> +{
> +    MachineState *machine = MACHINE(qdev_get_machine());
> +
> +    assert(!object_resolve_path(FW_CFG_PATH, NULL));
> +
> +    object_property_add_child(OBJECT(machine), FW_CFG_NAME, obj, NULL);
> +}
> +
>  static void fw_cfg_class_init(ObjectClass *klass, void *data)
>  {
>      DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -1034,6 +1039,7 @@ static const TypeInfo fw_cfg_info = {
>      .parent        = TYPE_SYS_BUS_DEVICE,
>      .abstract      = true,
>      .instance_size = sizeof(FWCfgState),
> +    .instance_init = fw_cfg_init,
>      .class_init    = fw_cfg_class_init,
>  };
>  
> 

Hopefully I'm not wrong :) , but this looks like a surprisingly
attractive solution to me. Basically it sinks the assertion and the link
creation into the qdev_create() calls of fw_cfg_init_io_dma() and
fw_cfg_init_mem_wide(), which is good, because the assert / linking
preserve their relative order to the realization (i.e., they keep
preceding it).

Reviewed-by: Laszlo Ersek <address@hidden>

Thanks
Laszlo