Re: [Xen-devel] [PATCH v2] xen-blkfront: remove type check from blkfront_setup_discard

[David Vrabel <david.vrabel@citrix.com>]

On 13/01/14 13:16, Jan Beulich wrote:
>>>> On 13.01.14 at 14:00, Ian Campbell <Ian.Campbell@citrix.com> wrote:
>> On Mon, 2014-01-13 at 12:34 +0000, Jan Beulich wrote:
>>>>>> On 13.01.14 at 13:01, Olaf Hering <olaf@aepfle.de> wrote:
>>>> On Mon, Jan 13, Jan Beulich wrote:
>>>>
>>>>> You can't do this in one go - the first two and the last one may be
>>>>> set independently (and are independent in their meaning), and
>>>>> hence need to be queried independently (xenbus_gather() fails
>>>>> on the first absent value).
>>>>
>>>> Yes, thats the purpose. Since the properties are required its an all or
>>>> nothing thing. If they are truly optional then blkif.h should be updated
>>>> to say that.
>>>
>>> They _are_ optional.
>>
>> But is it true that either they are all present or they are all absent?
> 
> No, it's not. discard-secure is independent of the other two (but
> those other two are tied together).

Can we have a patch to blkif.h that clarifies this?

e.g.,

feature-discard

   ...

   discard-granularity and discard-offset must also be present if
   feature-discard is enabled

   discard-secure may also be present if feature-discard is enabled.

David