Re: [PATCH RFC 2/9] IB/core: Introduce Signature Verbs API

[Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 10/22/2013 9:20 PM, Hefty, Sean wrote:
>>> Would we lose anything making this a new operation for the QP, versus
>> trying to hook it into the existing ib_post_send call?
>>
>> If I understand correctly you are suggesting making it a verb? Well this
>> operation is a fast-path operation - so I guess we will loose it in this
>> case.
>> Take SCSI for example, for each IO operation submitted by SCSI
>> mid-layer, transport layer should perform any protection policy that
>> SCSI asked for.
>>   From this point of view, signature operation resembles fast
>> registration (since the transport does not own the IOP data buffers, so
>> it uses fast registration methods).
>> That is why we are hooking into ib_post_send.
> I'm suggesting multiple calls that can post to the send queue, rather than one call that does a giant switch statement at the beginning based on the opcode.

Although I understand where you are coming from, We also lose in this case.
If we go down this rode, we block the user from saving a HW doorbell by 
concatenating signature and RDMA WRs to a post list.
I assume this is why fast_reg is also an extension of ib_post_send.

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