[openib-general] [PATCH] initial CM module

[Sean Hefty]

frank zago wrote:

>> +int ib_send_cm_req(struct ib_cm_id *cm_id,
>> +           struct ib_cm_req_param *param);
>> +

The Topspin API:
int ib_cm_connect(struct ib_cm_active_param  *param,
                   struct ib_path_record      *primary_path,
                   struct ib_path_record      *alternate_path,
                   tTS_IB_SERVICE_ID           service_id,
                   int                         peer_to_peer,
                   ib_cm_callback_func         function,
                   void                       *arg,
                   tTS_IB_CM_COMM_ID          *comm_id)

Main difference here is that the parameters have been folded into one. 
    (I'm not sure why ib_cm_active_param didn't just include the others.)

>> +int ib_send_cm_rep(struct ib_cm_id *cm_id,
>> +           struct ib_cm_req_param *param);

int ib_cm_accept(tTS_IB_CM_COMM_ID           comm_id,
                  struct ib_cm_passive_param *param)

Nearly identical.  Missing field was added to ib_cm_req_param that was 
lacking in ib_cm_passive_param.

>> +int ib_send_cm_rtu(struct ib_cm_id *cm_id,
>> +           void *private_data,
>> +           u8 private_data_len);

int ib_cm_confirm(tTS_IB_CM_COMM_ID comm_id,
                   void             *rtu_private_data,
                   int               rtu_private_data_len)

Same.

> 
> I've used several CM and I found this kind of interface to be painful to 
> use.
> I'd rather see an interface similar to Topspin's where you register a CM 
> callback, get CM events and react (or not) to these.

As pointed out above, this interface is similar to Topspin's.

> With the interface you propose it takes maybe 200 lines of code to 
> establish a simple connection, while with a callback it can be down to 
> 30 lines. It should be as easy as possible for an application or a 
> driver to establish a connection. I shouldn't have to rewrite a CM state 
> machine every time I need a connection.

This API does use a callback model based on events.  You register for a 
callback by calling ib_create_cm_id.

- Sean