On 12 July 2017 at 12:22, Markus Armbruster <arm...@redhat.com> wrote:
> Peter Maydell <peter.mayd...@linaro.org> writes:
>
>> In some situations it's useful to have a qdev property which doesn't
>> automatically set its default value when qdev_property_add_static is
>> called (for instance when the default value is not constant).
>>
>> Support this by adding a flag to the Property struct indicating
>> whether to set the default value. This replaces the existing test
>> for whether the PorpertyInfo set_default_value function pointer is
>
> PropertyInfo
>
>> NULL, and we set the .set_default field to true for all those cases
>> of struct Property which use a PropertyInfo with a non-NULL
>> set_default_value, so behaviour remains the same as before.
>>
>> We define two new macros DEFINE_PROP_SIGNED_NODEFAULT and
>> DEFINE_PROP_UNSIGNED_NODEFAULT, to cover the most plausible use cases
>> of wanting to set an integer property with no default value.
>
> Your text makes me wonder what is supposed to set the default value
> then. Glancing ahead to PATCH 3, it looks like method instance_init()
> is. Can you think of a scenario where something else sets it?
OK, proposed extra paragraph for commit message:
This gives us the semantics of:
* if .set_default is true and .info->set_default_value is not NULL,
then .defval is used as the the default value of the property
* otherwise, the property system does not set any default, and
the field will retain whatever initial value it was given by
the device's .instance_init method
(to go just before the "We define two new macros..." para.)
>> --- a/include/hw/qdev-core.h
>> +++ b/include/hw/qdev-core.h
>> @@ -226,6 +226,7 @@ struct Property {
>> PropertyInfo *info;
>> ptrdiff_t offset;
>> uint8_t bitnr;
>> + bool set_default;
>
> Your chance to add the very first comment to struct Property (its
> existing undocumentedness is an embarrassment, but not this patch's
> problem). Let's write down that this flag governs where (integer)
> default values come from, either from member devfal or from method
> instance_init() or whatever.
OK, how about
/**
* Property:
* @set_default: true if the default value should be set from @defval
* (if false then no default value is set by the property system
* and the field retains whatever value it was given by instance_init).
* @defval: default value for the property. This is used only if @set_default
* is true and @info->set_default_value is not NULL.
*/
?
thanks
-- PMM
