net/bnxt: fix backward firmware compatibility

[ upstream commit 589619999b0411a4266e335fe105e1c7cba6e02b ]

On older firmware versions, HWRM_FUNC_QCAPS response is not
returning the maximum number of multicast filters that can be
supported by the function. As a result, memory allocation with
size 0 fails.

Bugzilla ID: 1309

Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>

drivers/net/bnxt/bnxt.h

@@ -867,6 +867,7 @@ struct bnxt {
 	struct rte_ether_addr	*mcast_addr_list;
 	rte_iova_t		mc_list_dma_addr;
 	uint32_t		nb_mc_addr;
+#define BNXT_DFLT_MAX_MC_ADDR	16 /* for compatibility with older firmware */
 	uint32_t		max_mcast_addr; /* maximum number of mcast filters supported */
 
 	struct rte_eth_rss_conf	rss_conf; /* RSS configuration. */

drivers/net/bnxt/bnxt_hwrm.c

@@ -907,7 +907,8 @@ static int __bnxt_hwrm_func_qcaps(struct bnxt *bp)
 		    bp->max_l2_ctx, bp->max_vnics);
 	bp->max_stat_ctx = rte_le_to_cpu_16(resp->max_stat_ctx);
 	bp->max_mcast_addr = rte_le_to_cpu_32(resp->max_mcast_filters);
-
+	if (!bp->max_mcast_addr)
+		bp->max_mcast_addr = BNXT_DFLT_MAX_MC_ADDR;
 	if (BNXT_PF(bp)) {
 		bp->pf->total_vnics = rte_le_to_cpu_16(resp->max_vnics);
 		if (flags & HWRM_FUNC_QCAPS_OUTPUT_FLAGS_PTP_SUPPORTED) {