| Message ID | 20210304223431.15045-5-elder@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: qualcomm: rmnet: stop using C bit-fields | expand |
On Thu 04 Mar 16:34 CST 2021, Alex Elder wrote: > The actual layout of bits defined in C bit-fields (e.g. int foo : 3) > is implementation-defined. Structures defined in <linux/if_rmnet.h> > 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. Instead, define a single-byte > flags field, and use the functions defined in <linux/bitfield.h>, > along with field mask constants to extract or assign values within > that field. > Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> Regards, Bjorn > Signed-off-by: Alex Elder <elder@linaro.org> > --- > .../ethernet/qualcomm/rmnet/rmnet_handlers.c | 5 ++-- > .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 4 +++- > include/linux/if_rmnet.h | 23 ++++++++----------- > 3 files changed, 16 insertions(+), 16 deletions(-) > > diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c > index 2a6b2a609884c..30f8e2f02696b 100644 > --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c > +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c > @@ -4,6 +4,7 @@ > * RMNET Data ingress/egress handler > */ > > +#include <linux/bitfield.h> > #include <linux/netdevice.h> > #include <linux/netdev_features.h> > #include <linux/if_arp.h> > @@ -61,7 +62,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, > u16 len, pad; > u8 mux_id; > > - if (map_header->cd_bit) { > + if (u8_get_bits(map_header->flags, MAP_CMD_FMASK)) { > /* Packet contains a MAP command (not data) */ > if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS) > return rmnet_map_command(skb, port); > @@ -70,7 +71,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, > } > > mux_id = map_header->mux_id; > - pad = map_header->pad_len; > + pad = u8_get_bits(map_header->flags, MAP_PAD_LEN_FMASK); > 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 fd55269c2ce3c..3291f252d81b0 100644 > --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c > +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c > @@ -4,6 +4,7 @@ > * RMNET Data MAP protocol > */ > > +#include <linux/bitfield.h> > #include <linux/netdevice.h> > #include <linux/ip.h> > #include <linux/ipv6.h> > @@ -299,7 +300,8 @@ 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 = u8_encode_bits(padding, MAP_PAD_LEN_FMASK); > > return map_header; > } > diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h > index 8c7845baf3837..4824c6328a82c 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 <asm/byteorder.h>" > -#endif > - u8 mux_id; > - __be16 pkt_len; > + u8 flags; /* MAP_*_FMASK */ > + u8 mux_id; > + __be16 pkt_len; /* Length of packet, including pad */ > } __aligned(1); > > +/* rmnet_map_header flags field: > + * CMD: 1 = packet contains a MAP command; 0 = packet contains data > + * PAD_LEN: number of pad bytes following packet data > + */ > +#define MAP_CMD_FMASK GENMASK(7, 7) > +#define MAP_PAD_LEN_FMASK GENMASK(5, 0) > + > struct rmnet_map_dl_csum_trailer { > u8 reserved1; > #if defined(__LITTLE_ENDIAN_BITFIELD) > -- > 2.20.1 >
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c index 2a6b2a609884c..30f8e2f02696b 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c @@ -4,6 +4,7 @@ * RMNET Data ingress/egress handler */ +#include <linux/bitfield.h> #include <linux/netdevice.h> #include <linux/netdev_features.h> #include <linux/if_arp.h> @@ -61,7 +62,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, u16 len, pad; u8 mux_id; - if (map_header->cd_bit) { + if (u8_get_bits(map_header->flags, MAP_CMD_FMASK)) { /* Packet contains a MAP command (not data) */ if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS) return rmnet_map_command(skb, port); @@ -70,7 +71,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, } mux_id = map_header->mux_id; - pad = map_header->pad_len; + pad = u8_get_bits(map_header->flags, MAP_PAD_LEN_FMASK); 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 fd55269c2ce3c..3291f252d81b0 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c @@ -4,6 +4,7 @@ * RMNET Data MAP protocol */ +#include <linux/bitfield.h> #include <linux/netdevice.h> #include <linux/ip.h> #include <linux/ipv6.h> @@ -299,7 +300,8 @@ 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 = u8_encode_bits(padding, MAP_PAD_LEN_FMASK); return map_header; } diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h index 8c7845baf3837..4824c6328a82c 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 <asm/byteorder.h>" -#endif - u8 mux_id; - __be16 pkt_len; + u8 flags; /* MAP_*_FMASK */ + u8 mux_id; + __be16 pkt_len; /* Length of packet, including pad */ } __aligned(1); +/* rmnet_map_header flags field: + * CMD: 1 = packet contains a MAP command; 0 = packet contains data + * PAD_LEN: number of pad bytes following packet data + */ +#define MAP_CMD_FMASK GENMASK(7, 7) +#define MAP_PAD_LEN_FMASK GENMASK(5, 0) + struct rmnet_map_dl_csum_trailer { u8 reserved1; #if defined(__LITTLE_ENDIAN_BITFIELD)
The actual layout of bits defined in C bit-fields (e.g. int foo : 3) is implementation-defined. Structures defined in <linux/if_rmnet.h> 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. Instead, define a single-byte flags field, and use the functions defined in <linux/bitfield.h>, along with field mask constants to extract or assign values within that field. Signed-off-by: Alex Elder <elder@linaro.org> --- .../ethernet/qualcomm/rmnet/rmnet_handlers.c | 5 ++-- .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 4 +++- include/linux/if_rmnet.h | 23 ++++++++----------- 3 files changed, 16 insertions(+), 16 deletions(-) -- 2.20.1