From 16653c16d282e768763b2e8cc78f75df8fd53992 Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Mon, 15 Mar 2021 16:51:49 -0500 Subject: [PATCH] net: qualcomm: rmnet: use masks instead of C bit-fields The actual layout of bits defined in C bit-fields (e.g. int foo : 3) is implementation-defined. Structures defined in address this by specifying all bit-fields twice, to cover two possible layouts. I think this pattern is repetitive and noisy, and I find the whole notion of compiler "bitfield endianness" to be non-intuitive. Stop using C bit-fields for the command/data flag and the pad length fields in the rmnet_map structure, and define a single-byte flags field instead. Define a mask for the single-bit "command" flag, and another mask for the encoded pad length. The content of both fields can be accessed using a simple bitwise AND operation. Signed-off-by: Alex Elder Reviewed-by: Bjorn Andersson Reviewed-by: Alexander Duyck Signed-off-by: David S. Miller --- .../net/ethernet/qualcomm/rmnet/rmnet_handlers.c | 4 ++-- .../net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 4 +++- include/linux/if_rmnet.h | 23 ++++++++++------------ 3 files changed, 15 insertions(+), 16 deletions(-) diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c index 2a6b2a6..0be5ac7 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c @@ -61,7 +61,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, u16 len, pad; u8 mux_id; - if (map_header->cd_bit) { + if (map_header->flags & MAP_CMD_FLAG) { /* Packet contains a MAP command (not data) */ if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS) return rmnet_map_command(skb, port); @@ -70,7 +70,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, } mux_id = map_header->mux_id; - pad = map_header->pad_len; + pad = map_header->flags & MAP_PAD_LEN_MASK; len = ntohs(map_header->pkt_len) - pad; if (mux_id >= RMNET_MAX_LOGICAL_EP) diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c index 3af6836..e7d0394 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c @@ -280,6 +280,7 @@ struct rmnet_map_header *rmnet_map_add_map_header(struct sk_buff *skb, return map_header; } + BUILD_BUG_ON(MAP_PAD_LEN_MASK < 3); padding = ALIGN(map_datalen, 4) - map_datalen; if (padding == 0) @@ -293,7 +294,8 @@ struct rmnet_map_header *rmnet_map_add_map_header(struct sk_buff *skb, done: map_header->pkt_len = htons(map_datalen + padding); - map_header->pad_len = padding & 0x3F; + /* This is a data packet, so the CMD bit is 0 */ + map_header->flags = padding & MAP_PAD_LEN_MASK; return map_header; } diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h index 8c7845b..a02f0a3 100644 --- a/include/linux/if_rmnet.h +++ b/include/linux/if_rmnet.h @@ -6,21 +6,18 @@ #define _LINUX_IF_RMNET_H_ struct rmnet_map_header { -#if defined(__LITTLE_ENDIAN_BITFIELD) - u8 pad_len:6; - u8 reserved_bit:1; - u8 cd_bit:1; -#elif defined (__BIG_ENDIAN_BITFIELD) - u8 cd_bit:1; - u8 reserved_bit:1; - u8 pad_len:6; -#else -#error "Please fix " -#endif - u8 mux_id; - __be16 pkt_len; + u8 flags; /* MAP_CMD_FLAG, MAP_PAD_LEN_MASK */ + u8 mux_id; + __be16 pkt_len; /* Length of packet, including pad */ } __aligned(1); +/* rmnet_map_header flags field: + * PAD_LEN: number of pad bytes following packet data + * CMD: 1 = packet contains a MAP command; 0 = packet contains data + */ +#define MAP_PAD_LEN_MASK GENMASK(5, 0) +#define MAP_CMD_FLAG BIT(7) + struct rmnet_map_dl_csum_trailer { u8 reserved1; #if defined(__LITTLE_ENDIAN_BITFIELD) -- 2.7.4