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Re: [Qemu-arm] [Qemu-devel] [PATCH 1/3] qdev-properties.h: Explicitly se
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-arm] [Qemu-devel] [PATCH 1/3] qdev-properties.h: Explicitly set the default value for arraylen properties |
Date: |
Thu, 13 Jul 2017 18:21:50 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
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>
[Qemu-arm] [PATCH 2/3] qdev: support properties which don't set a default value, Peter Maydell, 2017/07/11