Re: [Qemu-devel] [PATCH RFC v2 03/12] VMState test: query command to extract the qdevified device names

[Eric Blake <eblake@redhat.com>]

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On 07/25/2014 09:39 AM, Sanidhya Kashyap wrote:
> I have provided a qmp interface for getting the list of qdevified devices
> that have been registered with SaveVMHandlers.
> 
> Signed-off-by: Sanidhya Kashyap <sanidhya.iiith@gmail.com>
> ---
>  qapi-schema.json | 22 ++++++++++++++++++++++
>  qmp-commands.hx  | 25 +++++++++++++++++++++++++
>  savevm.c         | 34 ++++++++++++++++++++++++++++++++++
>  3 files changed, 81 insertions(+)
> 

> +# @device: list of qdevified device names
> +#
> +# Since 2.2
> +##
> +{ 'type': 'VMStatesQdevDevices',
> +  'data': { 'device': ['str'] } }

Here, you name it 'device' [1]

> +
> +##
> +# @query-qdev-devices
> +#
> +# returns the VMStatesQdevDevices that have the associated value
> +#
> +# Since 2.2
> +##
> +{ 'command': 'query-qdev-devices',
> +  'returns': 'VMStatesQdevDevices' }

and state that it returns a single struct [2]

> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 4be4765..2e20032 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -3755,3 +3755,28 @@ Example:
>  <- { "return": {} }
>  
>  EQMP
> +
> +    {
> +        .name       = "query-qdev-devices",
> +        .args_type  = "",
> +        .mhandler.cmd_new = qmp_marshal_input_query_qdev_devices,
> +    },
> +
> +SQMP
> +query-qdev-devices
> +------------------
> +
> +Shows registered Qdevified devices
> +
> +
> +Example (1):
> +
> +-> { "execute": "query-qdev-devices" }
> +<- { "return": [

But here, your example shows it returning an array of structs [2]

> +       {
> +         "devices": [ "kvm-tpr-opt", "piix4_pm" ]

where each struct contains a member named 'devices' [1] that is also an
array.

I actually think the most extensible thing would be to return something
more like this QMP wire contents:

{ "return": [
  { "device": "kvm-tpr-opt" },
  { "device": "piix4_pm" }
] }

which would match this .json content:

{ 'type': 'VMStatesQdevDevices',
  'data': { 'device': 'str' } }
{ 'command': 'query-qdev-devices',
  'returns': [ 'VMStatesQdevDevices' ] }

and also be the most extensible for future tweaks, such as adding an
optional boolean flag to the json to tell us more about certain devices:

{ 'type': 'VMStatesQdevDevices',
  'data': { 'device': 'str', '*foo': 'bool' } }

and lead to this QMP wire transaction:

{ "return": [
  { "device": "kvm-tpr-opt" },
  { "device": "piix4_pm", 'foo': true }
] }


At any rate, you MUST make your example match your documentation.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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