[PATCH net-next v4 5/6] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum trailer

From: Alex Elder
Date: Mon Mar 15 2021 - 09:35:47 EST


Replace the use of C bit-fields in the rmnet_map_dl_csum_trailer
structure with a single one-byte field, using constant field masks
to encode or get at embedded values.

Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
v3: - Use BIT(x) and don't use u8_get_bits() for the checksum valid flag

.../ethernet/qualcomm/rmnet/rmnet_map_data.c | 2 +-
include/linux/if_rmnet.h | 17 +++++++----------
2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 3c3307949db00..3df23365497c4 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -365,7 +365,7 @@ int rmnet_map_checksum_downlink_packet(struct sk_buff *skb, u16 len)

csum_trailer = (struct rmnet_map_dl_csum_trailer *)(skb->data + len);

- if (!csum_trailer->valid) {
+ if (!(csum_trailer->flags & MAP_CSUM_DL_VALID_FLAG)) {
priv->stats.csum_valid_unset++;
return -EINVAL;
}
diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
index a02f0a3df1d9a..941997df9e088 100644
--- a/include/linux/if_rmnet.h
+++ b/include/linux/if_rmnet.h
@@ -19,21 +19,18 @@ struct rmnet_map_header {
#define MAP_CMD_FLAG BIT(7)

struct rmnet_map_dl_csum_trailer {
- u8 reserved1;
-#if defined(__LITTLE_ENDIAN_BITFIELD)
- u8 valid:1;
- u8 reserved2:7;
-#elif defined (__BIG_ENDIAN_BITFIELD)
- u8 reserved2:7;
- u8 valid:1;
-#else
-#error "Please fix <asm/byteorder.h>"
-#endif
+ u8 reserved1;
+ u8 flags; /* MAP_CSUM_DL_VALID_FLAG */
__be16 csum_start_offset;
__be16 csum_length;
__be16 csum_value;
} __aligned(1);

+/* rmnet_map_dl_csum_tra