Re: [PATCH 4/6] net/e1000: implement descriptor status API (em)

["Lu, Wenzhuo" <wenzhuo.lu@intel.com>]

Hi Oliver,

> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Thursday, March 2, 2017 1:19 AM
> To: dev@dpdk.org; thomas.monjalon@6wind.com; Ananyev, Konstantin; Lu,
> Wenzhuo; Zhang, Helin; Wu, Jingjing; adrien.mazarguil@6wind.com;
> nelio.laranjeiro@6wind.com
> Cc: Yigit, Ferruh; Richardson, Bruce
> Subject: [PATCH 4/6] net/e1000: implement descriptor status API (em)
> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> +int
> +eth_em_tx_descriptor_status(struct rte_eth_dev *dev, uint16_t tx_queue_id,
> +	uint16_t offset)
> +{
> +	volatile uint8_t *status;
> +	struct em_tx_queue *txq;
> +	uint32_t desc;
> +
> +	txq = dev->data->tx_queues[tx_queue_id];
> +	if (unlikely(offset >= txq->nb_tx_desc))
> +		return -EINVAL;
> +
> +	desc = txq->tx_tail + offset;
> +	/* go to next desc that has the RS bit */
> +	desc = ((desc + txq->tx_rs_thresh - 1) / txq->tx_rs_thresh) *
> +		txq->tx_rs_thresh;
The descriptor may be changed here. So the return value may not be for the offset one. Why?

> +	status = &txq->tx_ring[desc].upper.fields.status;
> +	if (*status & E1000_TXD_STAT_DD)
> +		return RTE_ETH_TX_DESC_DONE;
> +
> +	return RTE_ETH_TX_DESC_FULL;
> +}
> +
>  void
>  em_dev_clear_queues(struct rte_eth_dev *dev)  {
> --
> 2.8.1