Re: [PATCH 08/17] ssi: Add ssi_realize_and_unref()

[Philippe Mathieu-Daudé]

On 6/28/20 4:24 PM, Peter Maydell wrote:
> Add an ssi_realize_and_unref(), for the benefit of callers
> who want to be able to create an SSI device, set QOM properties
> on it, and then do the realize-and-unref afterwards.
> 
> The API works on the same principle as the recently added
> qdev_realize_and_undef(), sysbus_realize_and_undef(), etc.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/hw/ssi/ssi.h | 26 ++++++++++++++++++++++++++
>  hw/ssi/ssi.c         |  7 ++++++-
>  2 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/ssi/ssi.h b/include/hw/ssi/ssi.h
> index 93f2b8b0beb..4be5325e654 100644
> --- a/include/hw/ssi/ssi.h
> +++ b/include/hw/ssi/ssi.h
> @@ -79,6 +79,32 @@ extern const VMStateDescription vmstate_ssi_slave;
>  }
>  
>  DeviceState *ssi_create_slave(SSIBus *bus, const char *name);
> +/**
> + * ssi_realize_and_unref: realize and unref an SSI slave device
> + * @dev: SSI slave device to realize
> + * @bus: SSI bus to put it on
> + * @errp: error pointer
> + *
> + * Call 'realize' on @dev, put it on the specified @bus, and drop the
> + * reference to it. Errors are reported via @errp and by returning
> + * false.
> + *
> + * This function is useful if you have created @dev via qdev_new()
> + * (which takes a reference to the device it returns to you), so that
> + * you can set properties on it before realizing it. If you don't need
> + * to set properties then ssi_create_slave() is probably better (as it
> + * does the create, init and realize in one step).
> + *
> + * If you are embedding the SSI slave into another QOM device and
> + * initialized it via some variant on object_initialize_child() then
> + * do not use this function, because that family of functions arrange
> + * for the only reference to the child device to be held by the parent
> + * via the child<> property, and so the reference-count-drop done here
> + * would be incorrect.  (Instead you would want ssi_realize(), which
> + * doesn't currently exist but would be trivial to create if we had
> + * any code that wanted it.)
> + */
> +bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp);
>  
>  /* Master interface.  */
>  SSIBus *ssi_create_bus(DeviceState *parent, const char *name);
> diff --git a/hw/ssi/ssi.c b/hw/ssi/ssi.c
> index 67b48c31cd6..a35d7ebb266 100644
> --- a/hw/ssi/ssi.c
> +++ b/hw/ssi/ssi.c
> @@ -90,11 +90,16 @@ static const TypeInfo ssi_slave_info = {
>      .abstract = true,
>  };
>  
> +bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp)
> +{
> +    return qdev_realize_and_unref(dev, &bus->parent_obj, errp);
> +}
> +
>  DeviceState *ssi_create_slave(SSIBus *bus, const char *name)
>  {
>      DeviceState *dev = qdev_new(name);
>  
> -    qdev_realize_and_unref(dev, &bus->parent_obj, &error_fatal);
> +    ssi_realize_and_unref(dev, bus, &error_fatal);
>      return dev;
>  }
>  

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>