[PATCH net-next] net: mscc: allow extracting the FCS into the skb

[Antoine Tenart]

This patch adds support for the NETIF_F_RXFCS feature in the Mscc
Ethernet driver. This feature is disabled by default and allow an user
to request the driver not to drop the FCS and to extract it into the skb
for debugging purposes.

Signed-off-by: Antoine Tenart <antoine.tenart@xxxxxxxxxxx>
---
 drivers/net/ethernet/mscc/ocelot.c       | 2 +-
 drivers/net/ethernet/mscc/ocelot_board.c | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index 1a4f2bb48ead..eb5119e7e60b 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -1606,7 +1606,7 @@ int ocelot_probe_port(struct ocelot *ocelot, u8 port,
 	dev->ethtool_ops = &ocelot_ethtool_ops;
 	dev->switchdev_ops = &ocelot_port_switchdev_ops;
 
-	dev->hw_features |= NETIF_F_HW_VLAN_CTAG_FILTER;
+	dev->hw_features |= NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_RXFCS;
 	dev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
 
 	memcpy(dev->dev_addr, ocelot->base_mac, ETH_ALEN);
diff --git a/drivers/net/ethernet/mscc/ocelot_board.c b/drivers/net/ethernet/mscc/ocelot_board.c
index 3cdf63e35b53..245452a0f244 100644
--- a/drivers/net/ethernet/mscc/ocelot_board.c
+++ b/drivers/net/ethernet/mscc/ocelot_board.c
@@ -126,11 +126,16 @@ static irqreturn_t ocelot_xtr_irq_handler(int irq, void *arg)
 			len += sz;
 		} while (len < buf_len);
 
-		/* Read the FCS and discard it */
+		/* Read the FCS */
 		sz = ocelot_rx_frame_word(ocelot, grp, false, &val);
 		/* Update the statistics if part of the FCS was read before */
 		len -= ETH_FCS_LEN - sz;
 
+		if (unlikely(dev->features & NETIF_F_RXFCS)) {
+			buf = (u32 *)skb_put(skb, ETH_FCS_LEN);
+			*buf = val;
+		}
+
 		if (sz < 0) {
 			err = sz;
 			break;
-- 
2.17.1