[openib-general] Immediate data question

[Tang, Changqing]

Thank you. Other than using immediate data to send notification from one
end to the other of a QP, is there any other way to do this ? For
example, can I modify
QP state from RTS to other state on one end, and then the other end gets
some notification when I query the QP ?

--CQ


> -----Original Message-----
> From: Roland Dreier [mailto:rdreier at cisco.com] 
> Sent: Monday, February 05, 2007 4:09 PM
> To: Tang, Changqing
> Cc: Michael S. Tsirkin; openib-general at openib.org
> Subject: Re: Immediate data question
> 
>  > 	If I only want to send/recv 4 bytes with immediate data:
> 
> I assume you mean that you only want to send the 4 bytes of 
> immediate data, and nothing else.
> 
>  > On sender side:
>  > 	opcode = IBV_WR_SEND_WITH_IMM;
>  > 	imm_data = my_4_bytes_data;
>  > 
>  > 	Do I still need to specify sg_list and num_sge ?
> 
> Well, you should be able to specify num_sge = 0.  But to be 
> honest I'm not positive that 0-length sends are allowed; I 
> know that 0-length RDMA WRITE operations are allowed.
> 
>  > On receiver side, because the immediate data is inside the 
> completion  > structure, do I need to post a receive for 
> above message ?
> 
> Yes, otherwise how would you get the immediate data?
> 
>  > If I need to post a receive, do I need to specify sg_list 
> and num_sge  > for the receive ?
> 
> I believe that a 0-length receive with num_sge = 0 should be 
> fine, at least to handle an RDMA write with immediate data.  
> But again I'm not positive.
> 
>  - R.
>