cxgbe(4): Use t4_link_down_rc_str in shared code to decode the reason

the link is down, instead of doing it in OS specific code.

sys/dev/cxgbe/common/common.h

@@ -692,6 +692,7 @@ int t4_sge_ctxt_rd(struct adapter *adap, unsigned int mbox, unsigned int cid,
 int t4_sge_ctxt_rd_bd(struct adapter *adap, unsigned int cid, enum ctxt_type ctype,
 		      u32 *data);
 int t4_sge_ctxt_flush(struct adapter *adap, unsigned int mbox);
+const char *t4_link_down_rc_str(unsigned char link_down_rc);
 int t4_handle_fw_rpl(struct adapter *adap, const __be64 *rpl);
 int t4_fwaddrspace_write(struct adapter *adap, unsigned int mbox, u32 addr, u32 val);
 int t4_sched_config(struct adapter *adapter, int type, int minmaxen,

sys/dev/cxgbe/common/t4_hw.c

@@ -7429,6 +7429,31 @@ int t4_ofld_eq_free(struct adapter *adap, unsigned int mbox, unsigned int pf,
 	return t4_wr_mbox(adap, mbox, &c, sizeof(c), NULL);
 }
 
+/**
+ *	t4_link_down_rc_str - return a string for a Link Down Reason Code
+ *	@link_down_rc: Link Down Reason Code
+ *
+ *	Returns a string representation of the Link Down Reason Code.
+ */
+const char *t4_link_down_rc_str(unsigned char link_down_rc)
+{
+	static const char *reason[] = {
+		"Link Down",
+		"Remote Fault",
+		"Auto-negotiation Failure",
+		"Reserved3",
+		"Insufficient Airflow",
+		"Unable To Determine Reason",
+		"No RX Signal Detected",
+		"Reserved7",
+	};
+
+	if (link_down_rc >= ARRAY_SIZE(reason))
+		return "Bad Reason Code";
+
+	return reason[link_down_rc];
+}
+
 /**
  *	t4_handle_fw_rpl - process a FW reply message
  *	@adap: the adapter

sys/dev/cxgbe/t4_main.c

@@ -6020,10 +6020,6 @@ sysctl_linkdnrc(SYSCTL_HANDLER_ARGS)
 	int rc = 0;
 	struct port_info *pi = arg1;
 	struct sbuf *sb;
-	static const char *linkdnreasons[] = {
-		"non-specific", "remote fault", "autoneg failed", "reserved3",
-		"PHY overheated", "unknown", "rx los", "reserved7"
-	};
 
 	rc = sysctl_wire_old_buffer(req, 0);
 	if (rc != 0)
@@ -6034,10 +6030,8 @@ sysctl_linkdnrc(SYSCTL_HANDLER_ARGS)
 
 	if (pi->linkdnrc < 0)
 		sbuf_printf(sb, "n/a");
-	else if (pi->linkdnrc < nitems(linkdnreasons))
-		sbuf_printf(sb, "%s", linkdnreasons[pi->linkdnrc]);
 	else
-		sbuf_printf(sb, "%d", pi->linkdnrc);
+		sbuf_printf(sb, "%s", t4_link_down_rc_str(pi->linkdnrc));
 
 	rc = sbuf_finish(sb);
 	sbuf_delete(sb);