[dpdk-dev] [PATCH v2 4/4] ethdev: check driver support for functions

[Bruce Richardson <bruce.richardson@intel.com>]

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 run-time 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@intel.com>
---
 lib/librte_ether/rte_ethdev.h | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
index 1113ed2..0759de4 100644
--- a/lib/librte_ether/rte_ethdev.h
+++ b/lib/librte_ether/rte_ethdev.h
@@ -2608,16 +2608,18 @@ rte_eth_rx_burst(uint8_t port_id, uint16_t queue_id,
  * @param queue_id
  *  The queue id on the specific port.
  * @return
- *  The number of used descriptors in the specific queue.
+ *  The number of used descriptors in the specific queue, or:
+ *     (-EINVAL) if *port_id* is invalid
+ *     (-ENOTSUP) if the device does not support this function
  */
-static inline uint32_t
+static inline int
 rte_eth_rx_queue_count(uint8_t port_id, uint16_t queue_id)
 {
         struct rte_eth_dev *dev = &rte_eth_devices[port_id];
 #ifdef RTE_LIBRTE_ETHDEV_DEBUG
-	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, 0);
-	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_queue_count, 0);
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
 #endif
+	RTE_ETH_FPTR_OR_ERR_RET(*dev->dev_ops->rx_queue_count, -ENOTSUP);
         return (*dev->dev_ops->rx_queue_count)(dev, queue_id);
 }
 
@@ -2634,6 +2636,7 @@ 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)
@@ -2641,8 +2644,8 @@ rte_eth_rx_descriptor_done(uint8_t port_id, uint16_t queue_id, uint16_t offset)
 	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
 #ifdef RTE_LIBRTE_ETHDEV_DEBUG
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -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);
 }
-- 
2.4.3