Re: [Qemu-devel] qmp_device_add() ret_data argument

[Markus Armbruster]

Programmingkid <address@hidden> writes:

> What does the function qmp_device_add() have a ret_data argument if it
> isn't used? This function is located in qdev-monitor.c.

QMP command handlers all implement the same interface:

        void (*cmd_new)(QDict *params, QObject **ret_data, Error **errp);

Handlers of commands returning a value store the value to *ret_data.
Handlers of commands not returning a value (such as device_add) leave
ret_data alone.

We could require them to store NULL, but that would be easy to forget,
and usually catastrophic, so we don't.