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

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Message-Id: <20210315133455.1576188-6-elder@linaro.org>
Date:   Mon, 15 Mar 2021 08:34:54 -0500
From:   Alex Elder <elder@...aro.org>
To:     subashab@...eaurora.org, stranche@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org
Cc:     sharathv@...eaurora.org, bjorn.andersson@...aro.org,
        evgreen@...omium.org, cpratapa@...eaurora.org,
        David.Laight@...LAB.COM, olteanv@...il.com, elder@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next v4 5/6] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum trailer

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@...aro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---
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_trailer flags field:
+ *  VALID:	1 = checksum and length valid; 0 = ignore them
+ */
+#define MAP_CSUM_DL_VALID_FLAG		BIT(0)
+
 struct rmnet_map_ul_csum_header {
 	__be16 csum_start_offset;
 #if defined(__LITTLE_ENDIAN_BITFIELD)
-- 
2.27.0