Re: [Qemu-devel] [PATCH] Further tidy-up on block status

[Alex Bligh]

> On 13 Jan 2017, at 09:48, Vladimir Sementsov-Ogievskiy <address@hidden> wrote:
> 
> 12.01.2017 16:11, Alex Bligh wrote:
>>> On 12 Jan 2017, at 07:05, Vladimir Sementsov-Ogievskiy <address@hidden> 
>>> wrote:
>>> 
>>> Yes this is better. But is it actually needed to force contexts have some 
>>> safe default? If context wants it may define such default without this 
>>> requirement.. So, should it be requirement at all?
>> I've changed this to:
>> 
>>     of the file), a server MAY reply with a single block status
>>     descriptor with *length* matching the requested length, rather than
>>     reporting the error; in this case the context MAY mandate the
>>     status returned.
>> 
>> 
> 
> Hmm, I don't understand. So, it MAY mandate and therefore MAY NOT do it? And 
> what client should think, if server replies with one chunk matching the 
> request length and not mandate the status?

Some contexts may mandate a particular value (so for instance the allocation 
context might mandate 0).

Some contexts may not mandate a particular value, in which case the 
interpretation is dependent upon the context (just like any other status 
value). EG a context which returned an status of 7 if the range contained a 
prime number, and else 3, could carry on doing that.

As it doesn't make sense to interpret status returns without an understanding 
of the particular context, we might as well simply extend this to 'beyond the 
range' returns - as I think you pointed out!

-- 
Alex Bligh