Re: [Embedded-pv-devel] [PATCH v10] xen: add para-virtual sound interface header file

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.11.16 at 18:11, <andr2000@xxxxxxxxx> wrote:
>> > +struct xensnd_close_req {
>>> +};
>>
>> I'm afraid structures without any members aren't permitted by C89.
>>
> There are 2 options I see:
> 1. Remove empty structures
> 2. Leave them in, but add a comment and add a dummy place holder
> I would prefer option 1 as this way the interface seems to be clearer,
> like all requests are defined etc.

I'm not really sure which option is better, so I'd leave this to the
(soon to be sole) maintainer of those files (Konrad - I don't think
I've seen v2 of that patch yet).

>>> +struct xensnd_request {
>>> +     uint8_t raw[64];
>>> +};
>>> +
>>> +struct xensnd_response {
>>> +     uint8_t raw[64];
>>> +};
>>
>> What are these two needed for now? If you want to enforce a
>> minimum size, that would better go ...
>>
> That is because we want to be cache line aligned. What it means in practice
> is not clear as we have so many HW around, so it is not possible to
> fit all. So the options could be:
> 1. 32 or 64
> 2. 48 I think is not an option here
> I would stick to 32

I don't understand why you switched over to discussing size, when all
I've asked for is to change the placement of these size enforcing
constructs (after all by themselves they're not useful types).

Jan


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