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

[Bruce Richardson]

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
 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);
-- 
2.4.2