Replace the use of C bit-fields in the rmnet_map_ul_csum_header
structure with a single two-byte (big endian) structure member,
and use field masks to encode or get values within it.

Previously rmnet_map_ipv4_ul_csum_header() would update values in
the host byte-order fields, and then forcibly fix their byte order
using a combination of byte order operations and types.

Instead, just compute the value that needs to go into the new
structure member and save it with a simple byte-order conversion.

Make similar simplifications in rmnet_map_ipv6_ul_csum_header().

Finally, in rmnet_map_checksum_uplink_packet() a set of assignments
zeroes every field in the upload checksum header.  Replace that with
a single memset() operation.

Signed-off-by: Alex Elder <el...@linaro.org>
Reported-by: kernel test robot <l...@intel.com>
---
v2: Fixed to use u16_encode_bits() instead of be16_encode_bits().

 .../ethernet/qualcomm/rmnet/rmnet_map_data.c  | 34 ++++++-------------
 include/linux/if_rmnet.h                      | 21 ++++++------
 2 files changed, 21 insertions(+), 34 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c 
b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 29d485b868a65..b76ad48da7325 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -198,23 +198,19 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr,
                              struct rmnet_map_ul_csum_header *ul_header,
                              struct sk_buff *skb)
 {
-       __be16 *hdr = (__be16 *)ul_header;
        struct iphdr *ip4h = iphdr;
        u16 offset;
+       u16 val;
 
        offset = skb_transport_header(skb) - (unsigned char *)iphdr;
        ul_header->csum_start_offset = htons(offset);
 
-       ul_header->csum_insert_offset = skb->csum_offset;
-       ul_header->csum_enabled = 1;
+       val = u16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK);
        if (ip4h->protocol == IPPROTO_UDP)
-               ul_header->udp_ind = 1;
-       else
-               ul_header->udp_ind = 0;
+               val |= u16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK);
+       val |= u16_encode_bits(skb->csum_offset, MAP_CSUM_UL_OFFSET_FMASK);
 
-       /* Changing remaining fields to network order */
-       hdr++;
-       *hdr = htons((__force u16)*hdr);
+       ul_header->csum_info = htons(val);
 
        skb->ip_summed = CHECKSUM_NONE;
 
@@ -241,24 +237,19 @@ 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;
        struct ipv6hdr *ip6h = ip6hdr;
        u16 offset;
+       u16 val;
 
        offset = skb_transport_header(skb) - (unsigned char *)ip6hdr;
        ul_header->csum_start_offset = htons(offset);
 
-       ul_header->csum_insert_offset = skb->csum_offset;
-       ul_header->csum_enabled = 1;
-
+       val = u16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK);
        if (ip6h->nexthdr == IPPROTO_UDP)
-               ul_header->udp_ind = 1;
-       else
-               ul_header->udp_ind = 0;
+               val |= u16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK);
+       val |= u16_encode_bits(skb->csum_offset, MAP_CSUM_UL_OFFSET_FMASK);
 
-       /* Changing remaining fields to network order */
-       hdr++;
-       *hdr = htons((__force u16)*hdr);
+       ul_header->csum_info = htons(val);
 
        skb->ip_summed = CHECKSUM_NONE;
 
@@ -425,10 +416,7 @@ 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_ind = 0;
+       memset(ul_header, 0, sizeof(*ul_header));
 
        priv->stats.csum_sw++;
 }
diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
index 1fbb7531238b6..9ff09a2bcf9e1 100644
--- a/include/linux/if_rmnet.h
+++ b/include/linux/if_rmnet.h
@@ -33,17 +33,16 @@ struct rmnet_map_dl_csum_trailer {
 
 struct rmnet_map_ul_csum_header {
        __be16 csum_start_offset;
-#if defined(__LITTLE_ENDIAN_BITFIELD)
-       u16 csum_insert_offset:14;
-       u16 udp_ind:1;
-       u16 csum_enabled:1;
-#elif defined (__BIG_ENDIAN_BITFIELD)
-       u16 csum_enabled:1;
-       u16 udp_ind:1;
-       u16 csum_insert_offset:14;
-#else
-#error "Please fix <asm/byteorder.h>"
-#endif
+       __be16 csum_info;               /* MAP_CSUM_UL_*_FMASK */
 } __aligned(1);
 
+/* csum_info field:
+ *  OFFSET:    where (offset in bytes) to insert computed checksum
+ *  UDP:       1 = UDP checksum (zero checkum means no checksum)
+ *  ENABLED:   1 = checksum computation requested
+ */
+#define MAP_CSUM_UL_OFFSET_FMASK       GENMASK(13, 0)
+#define MAP_CSUM_UL_UDP_FMASK          GENMASK(14, 14)
+#define MAP_CSUM_UL_ENABLED_FMASK      GENMASK(15, 15)
+
 #endif /* !(_LINUX_IF_RMNET_H_) */
-- 
2.27.0

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