Re: [Qemu-arm] [Qemu-devel] [PATCH 1/3] qdev-properties.h: Explicitly set the default value for arraylen properties

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On 13 July 2017 at 15:11, Markus Armbruster <address@hidden> wrote:
>> Peter Maydell <address@hidden> writes:
>>
>>> In DEFINE_PROP_ARRAY, because we use a PropertyInfo (qdev_prop_arraylen)
>>> which has a .set_default_value member we will set the field to a default
>>> value. That default value will be zero, by the C rule that struct
>>> initialization sets unmentioned members to zero if at least one member
>>> is initialized. However it's clearer to state it explicitly.
>>>
>>> Signed-off-by: Peter Maydell <address@hidden>
>>> ---
>>> If my eyeball of the sources is correct, this is the only case we
>>> have of a Property struct that uses a PropertyInfo with a non-NULL
>>> .set_default_value but which doesn't explicitly set .defval.u.
>>> ---
>>>  include/hw/qdev-properties.h | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
>>> index 0604c33..36d040c 100644
>>> --- a/include/hw/qdev-properties.h
>>> +++ b/include/hw/qdev-properties.h
>>> @@ -110,6 +110,7 @@ extern PropertyInfo qdev_prop_arraylen;
>>>                            _arrayfield, _arrayprop, _arraytype) {        \
>>>          .name = (PROP_ARRAY_LEN_PREFIX _name),                          \
>>>          .info = &(qdev_prop_arraylen),                                  \
>>> +        .defval.u = 0,                                                  \
>>>          .offset = offsetof(_state, _field)                              \
>>>              + type_check(uint32_t, typeof_field(_state, _field)),       \
>>>          .arrayinfo = &(_arrayprop),                                     \
>>
>> Hmm.
>>
>> .info and .defval apply to the array *length*.
>> .info.set_default_value() is set_default_uint(), which uses .defval.u.
>> Setting it here is correct.
>>
>> The array *elements* are described by .arrayinfo.  There is no
>> .arraydefval, but that's okay, because .arrayinfo.set_default_value()
>> doesn't get called.  Correct?
>
> Correct. (There's no way to specify a default value for array properties.)

Thanks!

Reviewed-by: Markus Armbruster <address@hidden>