Re: [PATCH v9 09/10] admin: conformance clauses

[Cornelia Huck <cohuck@redhat.com>]

On Fri, Nov 25 2022, Jason Wang <jasowang@redhat.com> wrote:

> å 2022/11/24 16:36, Michael S. Tsirkin åé:
>> On Thu, Nov 24, 2022 at 02:51:21PM +0800, Jason Wang wrote:
>>> On Thu, Nov 24, 2022 at 5:08 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>>>> +The device MUST NOT fail a command solely because the buffers
>>>> +provided are shorter or longer than described in this
>>>> +specification.
>>> I may miss something but how can it work if the buffer is shorter?
>> driver does not care what's there.
>>
>> this is mostly for forward compatibility - we'll add more fields and
>> I don't want to explain separately that old drivers post
>> short buffers with less fields.
>
>
> For example:
>
> The patch said:
>
> struct virtio_admin_cmd_list {
>  ÂÂÂÂÂÂ /* Indicates which of the below fields were returned
>  ÂÂÂÂÂÂ le32 device_admin_cmds[];
> };
>
> Does it mean the query can still succeed even if there's no space for 
> virtio_admin_cmd_list in the writable buffer?

Can we pick an absolute minimum length? All drivers need to be able to
at least accommodate this one. Or is it ok for the driver to send a
completely useless query that doesn't get any data back?