netdev - [PATCH 4/8] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum header

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Date:   Mon, 20 May 2019 08:53:50 -0500
From:   Alex Elder <elder@...aro.org>
To:     arnd@...db.de, subashab@...eaurora.org, david.brown@...aro.org,
        agross@...nel.org, davem@...emloft.net
Cc:     bjorn.andersson@...aro.org, ilias.apalodimas@...aro.org,
        cpratapa@...eaurora.org, syadagir@...eaurora.org,
        evgreen@...omium.org, benchan@...gle.com, ejcaruso@...gle.com,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/8] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum header

Replace the use of C bit-fields in the rmnet_map_ul_csum_header
structure with a single integral structure member, and use field
masks to encode or get values within that member.

Note that the previous C bit-fields were defined with CPU local
endianness.  Their values were computed and then forecfully converted
to network byte order in rmnet_map_ipv4_ul_csum_header().  Simplify
that function, and properly define the new csum_info member as a big
endian value.

Make similar simplifications in rmnet_map_ipv6_ul_csum_header().

Signed-off-by: Alex Elder <elder@...aro.org>
---
 .../net/ethernet/qualcomm/rmnet/rmnet_map.h   |  9 ++--
 .../ethernet/qualcomm/rmnet/rmnet_map_data.c  | 50 ++++++++-----------
 2 files changed, 26 insertions(+), 33 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
index a56209645c81..f3231c26badd 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
@@ -60,11 +60,14 @@ struct rmnet_map_dl_csum_trailer {
 
 struct rmnet_map_ul_csum_header {
 	__be16 csum_start_offset;
-	u16 csum_insert_offset:14;
-	u16 udp_ip4_ind:1;
-	u16 csum_enabled:1;
+	__be16 csum_info;	/* RMNET_MAP_UL_* */
 } __aligned(1);
 
+/* NOTE:  These field masks are defined in CPU byte order */
+#define RMNET_MAP_UL_CSUM_INSERT_FMASK	GENMASK(13, 0)
+#define RMNET_MAP_UL_CSUM_UDP_FMASK	GENMASK(14, 14)   /* 0: IP; 1: UDP */
+#define RMNET_MAP_UL_CSUM_ENABLED_FMASK	GENMASK(15, 15)
+
 #define RMNET_MAP_COMMAND_REQUEST     0
 #define RMNET_MAP_COMMAND_ACK         1
 #define RMNET_MAP_COMMAND_UNSUPPORTED 2
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 10d2d582a9ce..72b64114505a 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -207,22 +207,18 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr,
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
-	struct iphdr *ip4h = (struct iphdr *)iphdr;
-	__be16 *hdr = (__be16 *)ul_header, offset;
+	struct iphdr *ip4h = iphdr;
+	u16 offset;
+	u16 val;
 
-	offset = htons((__force u16)(skb_transport_header(skb) -
-				     (unsigned char *)iphdr));
-	ul_header->csum_start_offset = offset;
-	ul_header->csum_insert_offset = skb->csum_offset;
-	ul_header->csum_enabled = 1;
+	offset = skb_transport_header(skb) - (unsigned char *)iphdr;
+	ul_header->csum_start_offset = htons(offset);
+
+	val = u16_encode_bits(skb->csum_offset, RMNET_MAP_UL_CSUM_INSERT_FMASK);
+	val |= RMNET_MAP_UL_CSUM_ENABLED_FMASK;
 	if (ip4h->protocol == IPPROTO_UDP)
-		ul_header->udp_ip4_ind = 1;
-	else
-		ul_header->udp_ip4_ind = 0;
-
-	/* Changing remaining fields to network order */
-	hdr++;
-	*hdr = htons((__force u16)*hdr);
+		val |= RMNET_MAP_UL_CSUM_UDP_FMASK;
+	ul_header->csum_info = htons(val);
 
 	skb->ip_summed = CHECKSUM_NONE;
 
@@ -249,18 +245,16 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr,
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
-	__be16 *hdr = (__be16 *)ul_header, offset;
+	u16 offset;
+	u16 val;
 
-	offset = htons((__force u16)(skb_transport_header(skb) -
-				     (unsigned char *)ip6hdr));
-	ul_header->csum_start_offset = offset;
-	ul_header->csum_insert_offset = skb->csum_offset;
-	ul_header->csum_enabled = 1;
-	ul_header->udp_ip4_ind = 0;
+	offset = skb_transport_header(skb) - (unsigned char *)ip6hdr;
+	ul_header->csum_start_offset = htons(offset);
 
-	/* Changing remaining fields to network order */
-	hdr++;
-	*hdr = htons((__force u16)*hdr);
+	val = u16_encode_bits(skb->csum_offset, RMNET_MAP_UL_CSUM_INSERT_FMASK);
+	val |= RMNET_MAP_UL_CSUM_ENABLED_FMASK;
+	/* Not UDP, so that field is 0 */
+	ul_header->csum_info = htons(val);
 
 	skb->ip_summed = CHECKSUM_NONE;
 
@@ -400,8 +394,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
 	struct rmnet_map_ul_csum_header *ul_header;
 	void *iphdr;
 
-	ul_header = (struct rmnet_map_ul_csum_header *)
-		    skb_push(skb, sizeof(struct rmnet_map_ul_csum_header));
+	ul_header = skb_push(skb, sizeof(*ul_header));
 
 	if (unlikely(!(orig_dev->features &
 		     (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM))))
@@ -428,10 +421,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
 	}
 
 sw_csum:
-	ul_header->csum_start_offset = 0;
-	ul_header->csum_insert_offset = 0;
-	ul_header->csum_enabled = 0;
-	ul_header->udp_ip4_ind = 0;
+	memset(ul_header, 0, sizeof(*ul_header));
 
 	priv->stats.csum_sw++;
 }
-- 
2.20.1