[dpdk-dev] [PATCH 4/4] ethdev: check support for rx_queue_count and descriptor_done fns

[Roger B. Melton]

Hi Bruce,  Comment in-line.  Regards, Roger

On 6/12/15 7:28 AM, Bruce Richardson wrote:
> The functions rte_eth_rx_queue_count and rte_eth_descriptor_done are
> supported by very few PMDs. Therefore, it is best to check for support
> for the functions in the ethdev library, so as to avoid crashes
> at run-time if the application goes to use those APIs. The performance
> impact of this change should be very small as this is a predictable
> branch in the function.
>
> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
> ---
>   lib/librte_ether/rte_ethdev.h | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
> index 827ca3e..9ad1b6a 100644
> --- a/lib/librte_ether/rte_ethdev.h
> +++ b/lib/librte_ether/rte_ethdev.h
> @@ -2496,6 +2496,8 @@ rte_eth_rx_burst(uint8_t port_id, uint16_t queue_id,
>    *  The queue id on the specific port.
>    * @return
>    *  The number of used descriptors in the specific queue.
> + *  NOTE: if function is not supported by device this call
> + *        returns (uint32_t)-ENOTSUP
>    */
>   static inline uint32_t

Why not change the return type to int32_t?
In this way, the caller isn't required to make the assumption that a 
large queue count indicates an error.  < 0 means error, other wise it's 
a valid queue count.

This approach would be consistent with other APIs.

>   rte_eth_rx_queue_count(uint8_t port_id, uint16_t queue_id)
> @@ -2507,8 +2509,9 @@ rte_eth_rx_queue_count(uint8_t port_id, uint16_t queue_id)
>   		RTE_PMD_DEBUG_TRACE("Invalid port_id=%d\n", port_id);
>   		return 0;
>   	}
> -	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_queue_count, 0);
>   #endif
> +	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_queue_count, (uint32_t)-ENOTSUP);
> +
>   	return (*dev->dev_ops->rx_queue_count)(dev, queue_id);
>   }
>   
> @@ -2525,6 +2528,7 @@ rte_eth_rx_queue_count(uint8_t port_id, uint16_t queue_id)
>    *  - (1) if the specific DD bit is set.
>    *  - (0) if the specific DD bit is not set.
>    *  - (-ENODEV) if *port_id* invalid.
> + *  - (-ENOTSUP) if the device does not support this function
>    */
>   static inline int
>   rte_eth_rx_descriptor_done(uint8_t port_id, uint16_t queue_id, uint16_t offset)
> @@ -2536,8 +2540,8 @@ rte_eth_rx_descriptor_done(uint8_t port_id, uint16_t queue_id, uint16_t offset)
>   		RTE_PMD_DEBUG_TRACE("Invalid port_id=%d\n", port_id);
>   		return -ENODEV;
>   	}
> -	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_descriptor_done, -ENOTSUP);
>   #endif
> +	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_descriptor_done, -ENOTSUP);
>   
>   	return (*dev->dev_ops->rx_descriptor_done)( \
>   		dev->data->rx_queues[queue_id], offset);

-- 
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|Roger B. Melton                |          |      Cisco Systems      |
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