[PATCH net-next v2] 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 a 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>
Reviewed-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
---

Since v1:
  - Rebased on top of the latest net-next.

 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 8f11fdba8d0e..9b8a17ee3cb3 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -1620,7 +1620,7 @@ 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 0cf0b0935b3b..4c23d18bbf44 100644
--- a/drivers/net/ethernet/mscc/ocelot_board.c
+++ b/drivers/net/ethernet/mscc/ocelot_board.c
@@ -128,11 +128,16 @@ 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