[dpdk-dev] [PATCH 1/6] ethdev: add descriptor status API

[Andrew Rybchenko]

On 03/01/2017 08:19 PM, Olivier Matz wrote:
> Introduce a new API to get the status of a descriptor.
>
> For Rx, it is almost similar to rx_descriptor_done API, except it
> differentiates "used" descriptors (which are hold by the driver and not
> returned to the hardware).
>
> For Tx, it is a new API.
>
> The descriptor_done() API, and probably the rx_queue_count() API could
> be replaced by this new API as soon as it is implemented on all PMDs.
>
> Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> ---
>   lib/librte_ether/rte_ethdev.h | 86 +++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 86 insertions(+)
>
> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
> index 97f3e2d..9ac9c61 100644
> --- a/lib/librte_ether/rte_ethdev.h
> +++ b/lib/librte_ether/rte_ethdev.h
> @@ -1179,6 +1179,14 @@ typedef uint32_t (*eth_rx_queue_count_t)(struct rte_eth_dev *dev,
>   typedef int (*eth_rx_descriptor_done_t)(void *rxq, uint16_t offset);
>   /**< @internal Check DD bit of specific RX descriptor */
>   
> +typedef int (*eth_rx_descriptor_status_t)(struct rte_eth_dev *dev,
> +	uint16_t rx_queue_id, uint16_t offset);
> +/**< @internal Check the status of a Rx descriptor */
> +
> +typedef int (*eth_tx_descriptor_status_t)(struct rte_eth_dev *dev,
> +	uint16_t tx_queue_id, uint16_t offset);
> +/**< @internal Check the status of a Tx descriptor */
> +
>   typedef int (*eth_fw_version_get_t)(struct rte_eth_dev *dev,
>   				     char *fw_version, size_t fw_size);
>   /**< @internal Get firmware information of an Ethernet device. */
> @@ -1483,6 +1491,10 @@ struct eth_dev_ops {
>   	eth_queue_release_t        rx_queue_release; /**< Release RX queue. */
>   	eth_rx_queue_count_t       rx_queue_count;/**< Get Rx queue count. */
>   	eth_rx_descriptor_done_t   rx_descriptor_done; /**< Check rxd DD bit. */
> +	eth_rx_descriptor_status_t rx_descriptor_status;
> +	/**< Check the status of a Rx descriptor. */
> +	eth_tx_descriptor_status_t tx_descriptor_status;
> +	/**< Check the status of a Tx descriptor. */
>   	eth_rx_enable_intr_t       rx_queue_intr_enable;  /**< Enable Rx queue interrupt. */
>   	eth_rx_disable_intr_t      rx_queue_intr_disable; /**< Disable Rx queue interrupt. */
>   	eth_tx_queue_setup_t       tx_queue_setup;/**< Set up device TX queue. */
> @@ -2768,6 +2780,80 @@ rte_eth_rx_descriptor_done(uint8_t port_id, uint16_t queue_id, uint16_t offset)
>   		dev->data->rx_queues[queue_id], offset);
>   }
>   
> +#define RTE_ETH_RX_DESC_AVAIL 0 /**< Desc available for hw. */
> +#define RTE_ETH_RX_DESC_DONE  1 /**< Desc done, filled by hw. */
> +#define RTE_ETH_RX_DESC_USED  2 /**< Desc used by driver. */
> +
> +/**
> + * Check the status of a Rx descriptor in the queue

I think it would be useful to highlight caller context.
Should it be the same CPU which receives packets from the queue?

> + *
> + * @param port_id
> + *  The port identifier of the Ethernet device.
> + * @param queue_id
> + *  The Rx queue identifier on this port.
> + * @param offset
> + *  The offset of the descriptor starting from tail (0 is the next
> + *  packet to be received by the driver).
> + * @return
> + *  - (RTE_ETH_DESC_AVAIL): Descriptor is available for the hardware to
> + *    receive a packet.
> + *  - (RTE_ETH_DESC_DONE): Descriptor is done, it is filled by hw, but
> + *    not yet processed by the driver (i.e. in the receive queue).
> + *  - (RTE_ETH_DESC_USED): Descriptor is unavailable (hold by driver,
> + *    not yet returned to hw).

It looks like it is the most suitable for descriptors which are reserved 
and never used.

> + *  - (-ENODEV) if *port_id* invalid.
> + *  - (-EINVAL) bad descriptor offset.
> + *  - (-ENOTSUP) if the device does not support this function.

What should be returned if queue_id is invalid?
What should be returned if the queue is stopped?

> + */
> +static inline int
> +rte_eth_rx_descriptor_status(uint8_t port_id, uint16_t queue_id,
> +	uint16_t offset)
> +{
> +	struct rte_eth_dev *dev;
> +
> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> +	dev = &rte_eth_devices[port_id];
> +	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->rx_descriptor_status, -ENOTSUP);
> +

May be it makes sense to range check queue_id here to avoid such code in 
each PMD?

> +	return (*dev->dev_ops->rx_descriptor_status)(dev, queue_id, offset);
> +}
> +
> +#define RTE_ETH_TX_DESC_FULL 0 /**< Desc filled by pmd for hw, waiting xmit. */
> +#define RTE_ETH_TX_DESC_DONE 1 /**< Desc done, packet is transmitted. */

I see no value suitable for descriptor which is never used.

> +/**
> + * Check the status of a Tx descriptor in the queue.
> + *
> + * @param port_id
> + *  The port identifier of the Ethernet device.
> + * @param queue_id
> + *  The Tx queue identifier on this port.
> + * @param offset
> + *  The offset of the descriptor starting from tail (0 is the place where
> + *  the next packet will be send).
> + *
> + * @return
> + *  - (RTE_ETH_DESC_FULL) Descriptor is being processed by the hw, i.e.
> + *    in the transmit queue.
> + *  - (RTE_ETH_DESC_DONE) Hardware is done with this descriptor, it can be
> + *    reused by the driver.
> + *  - (-ENODEV) if *port_id* invalid.
> + *  - (-EINVAL) bad descriptor offset.
> + *  - (-ENOTSUP) if the device does not support this function.
> + */
> +static inline int rte_eth_tx_descriptor_status(uint8_t port_id,
> +	uint16_t queue_id, uint16_t offset)
> +{
> +	struct rte_eth_dev *dev;
> +
> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> +	dev = &rte_eth_devices[port_id];
> +	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->tx_descriptor_status, -ENOTSUP);
> +
> +	return (*dev->dev_ops->tx_descriptor_status)(dev, queue_id, offset);
> +}
> +
>   /**
>    * Send a burst of output packets on a transmit queue of an Ethernet device.
>    *