ethdev: fix type and scope of variables in Rx burst

GCC 8.1 warned:

In function 'rte_eth_rx_burst':
rte_ethdev.h:3836:18: warning: conversion to 'int16_t'
{aka 'short int'} from 'uint16_t' {aka 'short unsigned int'}
may change the sign of the result [-Wsign-conversion]
  int16_t nb_rx = (*dev->rx_pkt_burst)(dev->data->rx_queues[queue_id],
                  ^
rte_ethdev.h:3844:50: warning: conversion to 'uint16_t'
{aka 'short unsigned int'} from 'int16_t' {aka 'short int'}
may change the sign of the result [-Wsign-conversion]
    nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
                                                  ^~~~~
rte_ethdev.h:3844:12: warning: conversion to 'int16_t'
{aka 'short int'} from 'uint16_t' {aka 'short unsigned int'}
may change the sign of the result [-Wsign-conversion]
    nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
            ^~
rte_ethdev.h:3851:9: warning: conversion to 'uint16_t'
{aka 'short unsigned int'} from 'int16_t' {aka 'short int'}
may change the sign of the result [-Wsign-conversion]
  return nb_rx;
         ^~~~~

The second part of the patch is solved by its own basic
block because it is inside a preprocessor conditional.

Bringing the declaration of the var to the top of the
function would require that also being given its own
preprocessor conditional, or a (void)var to avoid an
unused var warning.  The basic block is no worse than
those imho.

Fixes: 467465d86df1 ("ethdev: add packet count parameter to Rx callback")
Fixes: 4dc294158cac ("ethdev: support optional Rx and Tx callbacks")
Cc: stable@dpdk.org
Signed-off-by: Andy Green <andy@warmcat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index d52c1be..584af85 100644 (file)
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -3823,6 +3823,7 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t queue_id,
                 struct rte_mbuf **rx_pkts, const uint16_t nb_pkts)
 {
        struct rte_eth_dev *dev = &rte_eth_devices[port_id];
+       uint16_t nb_rx;
 
 #ifdef RTE_LIBRTE_ETHDEV_DEBUG
        RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, 0);
@@ -3833,13 +3834,14 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t queue_id,
                return 0;
        }
 #endif
-       int16_t nb_rx = (*dev->rx_pkt_burst)(dev->data->rx_queues[queue_id],
-                       rx_pkts, nb_pkts);
+       nb_rx = (*dev->rx_pkt_burst)(dev->data->rx_queues[queue_id],
+                                    rx_pkts, nb_pkts);
 
 #ifdef RTE_ETHDEV_RXTX_CALLBACKS
-       struct rte_eth_rxtx_callback *cb = dev->post_rx_burst_cbs[queue_id];
+       if (unlikely(dev->post_rx_burst_cbs[queue_id] != NULL)) {
+               struct rte_eth_rxtx_callback *cb =
+                               dev->post_rx_burst_cbs[queue_id];
 
-       if (unlikely(cb != NULL)) {
                do {
                        nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
                                                nb_pkts, cb->param);