Re: [PATCH rdma-core 2/2] libhns: Support cq record doorbell

["Liuyixian (Eason)" <liuyixian-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

On 2018/1/25 0:30, Jason Gunthorpe wrote:
> On Wed, Jan 24, 2018 at 01:51:41PM +0200, Leon Romanovsky wrote:
>> On Wed, Jan 24, 2018 at 06:35:20PM +0800, Liuyixian (Eason) wrote:
>>>
>>>
>>> On 2018/1/23 23:04, Jason Gunthorpe wrote:
>>>> On Tue, Jan 23, 2018 at 08:51:09PM +0800, Liuyixian (Eason) wrote:
>>>>> Could you please give me further comments on that email?  If you don't
>>>>> agree with what I said in that email, can you give some suggestions
>>>>> to resolve compatibility issue?
>>>>
>>>> You can't have a not compatible in your table.
>>>>
>>>> You need to add some kind of mechanism for userspace to enable the new
>>>> features conditionally.
>>>>
>>>> Jason
>>>>
>>> Thanks, I will consider your suggestion in next version patch set.
>>
>> ABI_VERSION cam help you to achieve that.
> 
> ABI_VERSION is mostly totally broken in verbs and breaks
> compatability with. It is a last emergency resort.
> 
> Probably in this case you just need to lengthen the response udata
> struct and the kernel can detect if the longer struct is provided to
> enable the feature and userspace can detect !0 to determine if the
> kernel supports it.
> 
> Jason

Okay, thanks both of you! I will fix the compatibility problem ASAP.

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