-----Original Message-----
From: Roland Dreier [mailto:roland@purestorage.com]
Sent: Wednesday, March 21, 2012 10:04 PM
To: Pandit, Parav
Cc: linux-rdma@vger.kernel.org; netdev@vger.kernel.org
Subject: Re: [PATCH 4/9] ocrdma: Driver for Emulex OneConnect RDMA
adapter

quoted

+int ocrdma_qp_state_machine(struct ocrdma_qp *qp, enum ib_qp_state
+new_ib_state,
+                           enum ib_qp_state *old_ib_state) {
+       unsigned long flags;
+       int status = 0;
+       enum ocrdma_qp_state new_state;
+       new_state = get_ocrdma_qp_state(new_ib_state);
+
+       /* sync with wqe and rqe posting */
+       spin_lock_irqsave(&qp->q_lock, flags);
+
+       if (old_ib_state)
+               *old_ib_state = get_ibqp_state(qp->state);
+       if (new_state == qp->state) {
+               spin_unlock_irqrestore(&qp->q_lock, flags);
+               return 1;
+       }
+
+       switch (qp->state) {
+       case OCRDMA_QPS_RST:
+               switch (new_state) {
+               case OCRDMA_QPS_RST:
+               case OCRDMA_QPS_INIT:
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_INIT:
+               /* qps: INIT->XXX */
+               switch (new_state) {
+               case OCRDMA_QPS_INIT:
+               case OCRDMA_QPS_RTR:
+                       break;
+               case OCRDMA_QPS_ERR:
+                       ocrdma_flush_qp(qp);
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_RTR:
+               /* qps: RTS->XXX */
+               switch (new_state) {
+               case OCRDMA_QPS_RTS:
+                       break;
+               case OCRDMA_QPS_ERR:
+                       ocrdma_flush_qp(qp);
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_RTS:
+               /* qps: RTS->XXX */
+               switch (new_state) {
+               case OCRDMA_QPS_SQD:
+               case OCRDMA_QPS_SQE:
+                       break;
+               case OCRDMA_QPS_ERR:
+                       ocrdma_flush_qp(qp);
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_SQD:
+               /* qps: SQD->XXX */
+               switch (new_state) {
+               case OCRDMA_QPS_RTS:
+               case OCRDMA_QPS_SQE:
+               case OCRDMA_QPS_ERR:
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_SQE:
+               switch (new_state) {
+               case OCRDMA_QPS_RTS:
+               case OCRDMA_QPS_ERR:
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       case OCRDMA_QPS_ERR:
+               /* qps: ERR->XXX */
+               switch (new_state) {
+               case OCRDMA_QPS_RST:
+                       break;
+               default:
+                       status = -EINVAL;
+                       break;
+               };
+               break;
+       default:
+               status = -EINVAL;
+               break;
+       };
+       if (!status)
+               qp->state = new_state;
+
+       spin_unlock_irqrestore(&qp->q_lock, flags);
+       return status;
+}

The switch statement here seems to largely reimpliment
ib_modify_qp_is_ok() (which is exported from the rdma midlayer).  Is there
some reason that doesn't work for your driver?  I'd rather fix / generalize the
core helper function instead of having something mostly duplicate in a
hardware driver.

Yes. Driver needs to put QP to flush state. So that appropriate CQEs can be returned during poll_cq() phase.
So state machine is implemented above.