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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id w22sm382145otm.73.2021.03.04.20.50.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Mar 2021 20:50:16 -0800 (PST) Date: Thu, 4 Mar 2021 22:50:14 -0600 From: Bjorn Andersson To: Alex Elder Cc: subashab@codeaurora.org, stranche@codeaurora.org, davem@davemloft.net, kuba@kernel.org, sharathv@codeaurora.org, evgreen@chromium.org, cpratapa@codeaurora.org, elder@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 4/6] net: qualcomm: rmnet: use field masks instead of C bit-fields Message-ID: References: <20210304223431.15045-1-elder@linaro.org> <20210304223431.15045-5-elder@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210304223431.15045-5-elder@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > 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 , > along with field mask constants to extract or assign values within > that field. > Reviewed-by: Bjorn Andersson Regards, Bjorn > Signed-off-by: Alex Elder > --- > .../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 > #include > #include > #include > @@ -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 > #include > #include > #include > @@ -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 " > -#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 >