[参考译文] TMS570LS1227：EMACRxIntISR RX 和 Tx 处理程序 API 引起令人困惑的语句

void EMACReceive(hdkif_t *hdkif)
{
  rxch_t *rxch_int;
  volatile emac_rx_bd_t *curr_bd, *curr_tail, *last_bd;

  /* The receive structure that holds data about a particular receive channel */
  rxch_int = &(hdkif->rxchptr);

  /* Get the buffer descriptors which contain the earliest filled data */
  /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
  curr_bd = rxch_int->active_head;
  /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
  last_bd = rxch_int->active_tail;

  /**
   * Process the descriptors as long as data is available
   * when the DMA is receiving data, SOP flag will be set
  */
  /*SAFETYMCUSW 28 D MR:NA <APPROVED> "Hardware status bit read check" */
  /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
  /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
  while((curr_bd->flags_pktlen & EMAC_BUF_DESC_SOP) == EMAC_BUF_DESC_SOP) {

      whilecnt1++;

    /* Start processing once the packet is loaded */
    /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
    /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */   
    if((curr_bd->flags_pktlen & EMAC_BUF_DESC_OWNER) != EMAC_BUF_DESC_OWNER) {

      /* this bd chain will be freed after processing */
      /*SAFETYMCUSW 71 S MR:17.6 <APPROVED> "Assigned pointer value has required scope." */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */
      rxch_int->free_head = curr_bd;

      /* Get the total length of the packet. curr_bd points to the start
       * of the packet.
       */

      /* 
       * The loop runs till it reaches the end of the packet.
       */
      /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */          
      while((curr_bd->flags_pktlen & EMAC_BUF_DESC_EOP)!= EMAC_BUF_DESC_EOP)
      {
        /*Update the flags for the descriptor again and the length of the buffer*/
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        curr_bd->flags_pktlen = (uint32)EMAC_BUF_DESC_OWNER;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        curr_bd->bufoff_len = (uint32)MAX_TRANSFER_UNIT;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        last_bd = curr_bd;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        curr_bd = curr_bd->next;
        printf("whilecnt1 =%d\n\r",whilecnt1);

        countp++;

      }
      mg_tcpip_qwrite((void*)curr_bd->bufptr,curr_bd->bufoff_len, s_ifp);


      /* Updating the last descriptor (which contained the EOP flag) */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */          
        curr_bd->flags_pktlen = (uint32)EMAC_BUF_DESC_OWNER;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        curr_bd->bufoff_len = (uint32)MAX_TRANSFER_UNIT;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        last_bd = curr_bd;
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        curr_bd = curr_bd->next;

      /* Acknowledge that this packet is processed */
      /*SAFETYMCUSW 439 S MR:11.3 <APPROVED> "Address stored in pointer is passed as as an int parameter. - Advisory as per MISRA" */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
      EMACRxCPWrite(hdkif->emac_base, (uint32)EMAC_CHANNELNUMBER, (uint32)last_bd);

      /* The next buffer descriptor is the new head of the linked list. */
      /*SAFETYMCUSW 71 S MR:17.6 <APPROVED> "Assigned pointer value has required scope." */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
      rxch_int->active_head = curr_bd;

      /* The processed descriptor is now the tail of the linked list. */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
      curr_tail = rxch_int->active_tail;
    /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
      curr_tail->next = rxch_int->free_head;

      /* The last element in the already processed Rx descriptor chain is now the end of list. */
      /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */     
      last_bd->next = NULL;


        /**
         * Check if the reception has ended. If the EOQ flag is set, the NULL
         * Pointer is taken by the DMA engine. So we need to write the RX HDP
         * with the next descriptor.
         */
        /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */ 
        /*SAFETYMCUSW 134 S MR:12.2 <APPROVED> "LDRA Tool issue" */
      /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */            
        if((curr_tail->flags_pktlen & EMAC_BUF_DESC_EOQ) == EMAC_BUF_DESC_EOQ) {
          /*SAFETYMCUSW 439 S MR:11.3 <APPROVED> "Address stored in pointer is passed as as an int parameter. - Advisory as per MISRA" */
          /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */             
          EMACRxHdrDescPtrWrite(hdkif->emac_base, (uint32)(rxch_int->free_head), (uint32)EMAC_CHANNELNUMBER);
        }

        /*SAFETYMCUSW 71 S MR:17.6 <APPROVED> "Assigned pointer value has required scope." */
        /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */   
        /*SAFETYMCUSW 45 D MR:21.1 <APPROVED> "Valid non NULL input parameters are assigned in this driver" */   
        rxch_int->free_head  = curr_bd;
        rxch_int->active_tail = last_bd;
      }
    }
  whilecnt1=0;
}