Subject: [net-next PATCH 05/11] net: ravb: Simplify types in RX csum validation

From: Paul Barker <[email-masked]>
Date: Mon, 30 Sep 2024 17:08:39 +0100

From: Paul Barker <[email-masked]>

The HW checksum value is used as a 16-bit flag, it is zero when the
checksum has been validated and non-zero otherwise. Therefore we don't
need to treat this as an actual __wsum type or call csum_unfold(), we
can just use a u16 pointer.

Signed-off-by: Paul Barker <[email-masked]>
---
 drivers/net/ethernet/renesas/ravb_main.c | 30 +++++++++++-------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 1dd2152734b0..9350ca10ab22 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -749,12 +749,11 @@ static void ravb_get_tx_tstamp(struct net_device *ndev)
 static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 {
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
-	__wsum csum_proto;
-	skb_frag_t *last_frag;
-	u8 *hw_csum;
+	size_t csum_len;
+	u16 *hw_csum;
 
-	/* The hardware checksum status is contained in sizeof(__sum16) * 2 = 4
-	 * bytes appended to packet data.
+	/* The hardware checksum status is contained in 4 bytes appended to
+	 * packet data.
 	 *
 	 * For ipv4, the first 2 bytes are the ip header checksum status. We can
 	 * ignore this as it will always be re-checked in inet_gro_receive().
@@ -762,23 +761,22 @@ static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 	 * The last 2 bytes are the protocol checksum status which will be zero
 	 * if the checksum has been validated.
 	 */
-	if (unlikely(skb->len < sizeof(__sum16) * 2))
+	csum_len = sizeof(*hw_csum) * 2;
+	if (unlikely(skb->len < csum_len))
 		return;
 
 	if (skb_is_nonlinear(skb)) {
-		last_frag = &shinfo->frags[shinfo->nr_frags - 1];
-		hw_csum = skb_frag_address(last_frag) +
-			  skb_frag_size(last_frag);
-		skb_frag_size_sub(last_frag, 2 * sizeof(__sum16));
+		skb_frag_t *last_frag = &shinfo->frags[shinfo->nr_frags - 1];
+
+		hw_csum = (u16 *)(skb_frag_address(last_frag) +
+				  skb_frag_size(last_frag));
+		skb_frag_size_sub(last_frag, csum_len);
 	} else {
-		hw_csum = skb_tail_pointer(skb);
-		skb_trim(skb, skb->len - 2 * sizeof(__sum16));
+		hw_csum = (u16 *)skb_tail_pointer(skb);
+		skb_trim(skb, skb->len - csum_len);
 	}
 
-	hw_csum -= sizeof(__sum16);
-	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
-
-	if (!csum_proto)
+	if (!*--hw_csum)
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 }
 
-- 
2.43.0