Michael S. Tsirkin wrote:
There's also something I don't understand: ib_mad_recv_done_handler seems
to *always* pass response to ib_mad_post_receive_mads, even if
driver's process_mad returned IB_MAD_RESULT_CONSUMED: we simply
do "goto out" and that has
if (response) {
ib_mad_post_receive_mads(qp_info, response);
Could you explain please?
I guess the naming is what confuses me: if this is a response, apparently
returned by driver, why are we passing it to ib_mad_post_receive_mads?
The response MAD contains the data to send in reply to a received MAD. If
process_mad() returns CONSUMED, then the received MAD has been consumed and no
response was generated. If process_mad() returns REPLY, then the reply data is
in response->mad.mad. The data is copied to an ib_mad_send_buf in
agent_send_response().
Following what I believe is the common processing flow:
1. We receive a MAD.
2. We allocate a buffer to store a response from the device.
3. We call process_mad() to let the device examine the MAD.
4. The device will typically not process the MAD.
5. We hand the received MAD to a MAD agent.
6. We post a new receive on the special QP.
The code has been optimized to use the buffer allocated in step 2 as the receive
buffer in step 6.
- Sean
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