[openib-general] Some ib_mad.h Redirection Comments

[Hal Rosenstock]

On Mon, 2004-08-09 at 21:36, Sean Hefty wrote: 
> I've updated ib_mad.h (again).  This time additional comments were added, 
> and notes were made where we need to continue or start having discussions.  
> The only major change to the API was modifying ib_mad_recv_wc to use a single receive buffer, 
> versus a chain.  
Is it intended that this structure include a pointer to the MAD (struct
ib_mad *mad) rather than a coalesced buffer and a (total) length ? 

I presume it is a requirement (of the implementation) that out of order
RMPP segments are reordered before presentation across this interface. 

> (I haven't given up on zero-copy receives; the proposed chaining just needs some additional thought.) 
> Hopefully, we can begin working towards this API, but continue discussing some of the areas marked 
> in the file with 'XXX'.
Maybe these should be in a GSI TODO rather than in this file. 

> I need to think more about the redirection case, and examine an implementation to see 
> how much work/policy is in it.  I think that if it is totally transparent to the requestor, 
> then the API will be unaffected.  Likewise, if it is exposed.  We probably only need to 
> modify the API if we need to reach some sort of compromise between the implementation 
> versus the policy.
At this point, in the interest of moving on, we ought to defer redirect.
We can live without it in the short term. 

> 
> Modified file is below:
> 

> struct ib_rmpp_hdr {
> 	u8	rmpp_version;
> 	u8	rmpp_type;
> 	u8	rmpp_flags;

As this field also contains RespTime, maybe it's name should be something
more like rmpp_rtime_flags.

> 	u8	rmpp_status;
> 	u32	seg_num;
> 	u32	paylen_newwin;
> } __attribute__ ((packed));

-- Hal