linux-kernel - [PATCH net-next 2/8] net: qualcomm: rmnet: rearrange some NOTs

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Date:   Sat, 12 Jun 2021 09:37:30 -0500
From:   Alex Elder <elder@...aro.org>
To:     subashab@...eaurora.org, stranche@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next 2/8] net: qualcomm: rmnet: rearrange some NOTs

With the ones' complement arithmetic, the sum of two negated values
is equal to the negation of the sum of the two original values [1].
Rearrange the calculation ip6_payload_sum using this property.

[1] https://tools.ietf.org/html/rfc1071

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 3e6feef0fd252..1b170e9189d8a 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -140,8 +140,8 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
 	 * checksum computed over the pseudo header.
 	 */
 	ip_header_csum = (__force __be16)ip_fast_csum(ip6h, sizeof(*ip6h) / 4);
-	ip6_payload_csum = csum16_sub((__force __sum16)~csum_trailer->csum_value,
-				      ~ip_header_csum);
+	ip6_payload_csum = ~csum16_sub((__force __sum16)csum_trailer->csum_value,
+				       ip_header_csum);
 
 	length = (ip6h->nexthdr == IPPROTO_UDP) ?
 		 ntohs(((struct udphdr *)txporthdr)->len) :
-- 
2.27.0