net: dsa: microchip: ksz8: Refactor ksz8_fdb_dump()

Refactor ksz8_fdb_dump() to address potential issues:
- Limit the number of iterations to avoid endless loops.
- Handle error codes returned by ksz8_r_dyn_mac_table(), with
  an exception for -ENXIO when no more dynamic entries are detected.

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Link: https://lore.kernel.org/r/20240403125039.3414824-4-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/microchip/ksz8795.c

@@ -1191,27 +1191,30 @@ void ksz8_flush_dyn_mac_table(struct ksz_device *dev, int port)
 int ksz8_fdb_dump(struct ksz_device *dev, int port,
 		  dsa_fdb_dump_cb_t *cb, void *data)
 {
-	int ret = 0;
-	u16 i = 0;
-	u16 entries = 0;
-	u8 fid;
-	u8 src_port;
 	u8 mac[ETH_ALEN];
+	u8 src_port, fid;
+	u16 entries = 0;
+	int ret, i;
 
-	do {
+	for (i = 0; i < KSZ8_DYN_MAC_ENTRIES; i++) {
 		ret = ksz8_r_dyn_mac_table(dev, i, mac, &fid, &src_port,
 					   &entries);
-		if (!ret && port == src_port) {
+		if (ret == -ENXIO)
+			return 0;
+		if (ret)
+			return ret;
+
+		if (i >= entries)
+			return 0;
+
+		if (port == src_port) {
 			ret = cb(mac, fid, false, data);
 			if (ret)
-				break;
+				return ret;
 		}
-		i++;
-	} while (i < entries);
-	if (i >= entries)
-		ret = 0;
+	}
 
-	return ret;
+	return 0;
 }
 
 static int ksz8_add_sta_mac(struct ksz_device *dev, int port,

drivers/net/dsa/microchip/ksz8795_reg.h

@@ -794,5 +794,6 @@
 #define TAIL_TAG_LOOKUP			BIT(7)
 
 #define FID_ENTRIES			128
+#define KSZ8_DYN_MAC_ENTRIES		1024
 
 #endif