Corey Bryant <cor...@linux.vnet.ibm.com> writes:
> On 03/19/2013 03:26 AM, Markus Armbruster wrote:
>> [Note cc: Anthony for QAPI schema expertise]
>>
>> Stefan Berger <stef...@linux.vnet.ibm.com> writes:
>>
>>> On 03/18/2013 12:16 PM, Markus Armbruster wrote:
>>>> Corey Bryant <cor...@linux.vnet.ibm.com> writes:
>>>>
>>>>> Signed-off-by: Corey Bryant <cor...@linux.vnet.ibm.com>
>>>>> ---
>>>>> qemu-options.hx | 3 ++-
>>>>> qmp-commands.hx | 59
>>>>> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>> 2 files changed, 61 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/qemu-options.hx b/qemu-options.hx
>>>>> index 30fb85d..3b3cd0f 100644
>>>>> --- a/qemu-options.hx
>>>>> +++ b/qemu-options.hx
>>>>> @@ -2237,7 +2237,8 @@ Backend type must be:
>>>>> @option{passthrough}.
>>>>> The specific backend type will determine the applicable
>>>>> options.
>>>>> -The @code{-tpmdev} option requires a @code{-device} option.
>>>>> +The @code{-tpmdev} option creates the TPM backend and requires a
>>>>> +@code{-device} option that specifies the TPM frontend interface model.
>>>>> Options to each backend are described below.
>>>>> diff --git a/qmp-commands.hx b/qmp-commands.hx
>>>>> index b370060..4eda5ea 100644
>>>>> --- a/qmp-commands.hx
>>>>> +++ b/qmp-commands.hx
>>>>> @@ -2721,18 +2721,77 @@ EQMP
>>>>> .mhandler.cmd_new = qmp_marshal_input_query_tpm,
>>>>> },
>>>>> +SQMP
>>>>> +query-tpm
>>>>> +---------
>>>>> +
>>>>> +Return information about the TPM device.
>>>>> +
>>>>> +Arguments: None
>>>>> +
>>>>> +Example:
>>>>> +
>>>>> +-> { "execute": "query-tpm" }
>>>>> +<- { "return":
>>>>> + [
>>>>> + { "model": "tpm-tis",
>>>>> + "tpm-options":
>>>>> + { "type": "tpm-passthrough-options",
>>>>> + "data":
>>>>> + { "cancel-path": "/sys/class/misc/tpm0/device/cancel",
>>>>> + "path": "/dev/tpm0"
>>>>> + }
>>>>> + },
>>>>> + "type": "passthrough",
>>>>> + "id": "tpm0"
>>>>> + }
>>>>> + ]
>>>>> + }
>>>>> +
>>>>> +EQMP
>>>>> +
>>>> "tpm-options" is a discriminated union. How is its discriminator "type"
>>>> (here: "tpm-passthrough-options") related to the outer "type" (here:
>>>> "passthrough")?
>>>
>>> It gives you similar information twice. So there is a direct
>>> relationship between the two types.
>>
>> Awkward and undocumented.
>>
>> Relevant parts of qapi-schema.json:
>>
>> { 'enum': 'TpmType', 'data': [ 'passthrough' ] }
>>
>> { 'union': 'TpmTypeOptions',
>> 'data': { 'tpm-passthrough-options' : 'TPMPassthroughOptions' } }
>>
>> { 'type': 'TPMInfo',
>> 'data': {'id': 'str',
>> 'model': 'TpmModel',
>> 'type': 'TpmType',
>> 'tpm-options': 'TpmTypeOptions' } }
>>
>> Type Netdev solves the same problem more elegantly:
>>
>> { 'union': 'NetClientOptions',
>> 'data': {
>> 'none': 'NetdevNoneOptions',
>> 'nic': 'NetLegacyNicOptions',
>> 'user': 'NetdevUserOptions',
>> 'tap': 'NetdevTapOptions',
>> 'socket': 'NetdevSocketOptions',
>> 'vde': 'NetdevVdeOptions',
>> 'dump': 'NetdevDumpOptions',
>> 'bridge': 'NetdevBridgeOptions',
>> 'hubport': 'NetdevHubPortOptions' } }
>>
>> { 'type': 'Netdev',
>> 'data': {
>> 'id': 'str',
>> 'opts': 'NetClientOptions' } }
>>
>> Uses the union's discriminator. Straightforward.
>>
>> Following Netdev precedence, we get:
>>
>> { 'union': 'TpmTypeOptions',
>> 'data': { 'passthrough' : 'TPMPassthroughOptions' } }
>>
>> { 'type': 'TPMInfo',
>> 'data': {'id': 'str',
>> 'model': 'TpmModel',
>> 'opts': 'TpmTypeOptions' } }
>>
>
> I can send a patch for this update if you'd like.
Yes, please!
>> Duplication of type is gone. No need for documentation.
>>
>> Since enum TpmType is used elsewhere, it still gets duplicated in the
>> union's discriminator. Anthony, is there a way to name the implicit
>> discriminator enum type for reference elsewhere in the schema?
>>
>
> Are you saying it still gets duplicated with this fix? I'm not sure
> what you mean.
A union in the schema implicitely defines an C enumeration type to be
used for its discriminator. For instance, union TpmTypeOptions
implicitely defines this one:
typedef enum TpmTypeOptionsKind
{
TPM_TYPE_OPTIONS_KIND_TPM_PASSTHROUGH_OPTIONS = 0,
TPM_TYPE_OPTIONS_KIND_MAX = 1,
} TpmTypeOptionsKind;
QAPI's discriminated union becomes a C struct containing the
discriminator and the union of the members:
struct TpmTypeOptions
{
TpmTypeOptionsKind kind;
union {
void *data;
TPMPassthroughOptions * tpm_passthrough_options;
};
};
Enum TpmType and type TpmInfo become:
typedef enum TpmType
{
TPM_TYPE_PASSTHROUGH = 0,
TPM_TYPE_MAX = 1,
} TpmType;
struct TPMInfo
{
char * id;
TpmModel model;
TpmType type;
TpmTypeOptions * tpm_options;
};
With the change I propose, TPM_TYPE_OPTIONS_KIND_TPM_PASSTHROUGH_OPTIONS
becomes TPM_TYPE_OPTIONS_KIND_TPM_PASSTHROUGH, and TPMInfo member type
goes away.
Because TpmType is still used elsewhere, it doesn't go away, thus still
duplicates TpmTypeOptionsKind. My question to Anthony was about ways to
avoid that remaining bit of duplication. I don't expect you do answer
it :)
