Re: [Qemu-devel] [PATCH v2 2/6] qapi: support nested structs in OptsVisitor

["Kővágó Zoltán" <dirty.ice.hu@gmail.com>]

2015-06-17 15:41 keltezéssel, Markus Armbruster írta:
> "Kővágó Zoltán" <dirty.ice.hu@gmail.com> writes:
>
>> 2015-06-17 13:18 keltezéssel, Markus Armbruster írta:
>>> Copying Kevin because similar issues exist in the block layer.
>>>
>>> Gerd Hoffmann <kraxel@redhat.com> writes:
>>>
>>>> On Mi, 2015-06-17 at 09:50 +0200, Markus Armbruster wrote:
>>>>> Copying László because his fingerprints are on OptsVisitor.
>>>>>
>>>>> "Kővágó, Zoltán" <dirty.ice.hu@gmail.com> writes:
>>>>>
>>>>>> The current OptsVisitor flattens the whole structure, if there are
>>>>>> same named
>>>>>> fields under different paths (like `in' and `out' in `Audiodev'),
>>>>>> the current
>>>>>> visitor can't cope with them (for example setting
>>>>>> frequency=44100' will set the
>>>>>> in's frequency to 44100 and leave out's frequency unspecified).
>>>>>>
>>>>>> This patch fixes it, by the following changes:
>>>>>> 1) Specifying just the field name will apply to all fields that has the
>>>>>>      specified name (this means it would set both in's and out's
>>>>>> frequency to
>>>>>>      44100 in the above example).
>>>
>>> What if they have different types?
>>>
>>> What if one of them can't take the value?
>>
>> Currently it will error out, requiring the user to be more
>> explicit. Probably not the best solution, but I can't really think of
>> a better solution. (If we would ignore invalid values that would be
>> very confusing imho.)
>
> Yes, we clearly don't want foo=0 to set a.foo and b.foo, but foo=x set
> only a.foo, because the former can take any string, but the latter only
> a number.
>
> Can we require the LHS to be unambiguous?

Originally I designed it that way because it allows you to specify 
frequency=44100 and set both in.frequency and out.frequency. But this 
could also be the convenience feature that we not really need. I don't 
see any other downside of making it unambigous.