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![Alex Elder](/assets/img/avatar_default.png)
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, 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 <elder@linaro.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
52 lines
1.2 KiB
C
52 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only
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* Copyright (c) 2013-2019, The Linux Foundation. All rights reserved.
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*/
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#ifndef _LINUX_IF_RMNET_H_
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#define _LINUX_IF_RMNET_H_
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struct rmnet_map_header {
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u8 flags; /* MAP_CMD_FLAG, MAP_PAD_LEN_MASK */
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u8 mux_id;
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__be16 pkt_len; /* Length of packet, including pad */
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} __aligned(1);
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/* rmnet_map_header flags field:
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* PAD_LEN: number of pad bytes following packet data
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* CMD: 1 = packet contains a MAP command; 0 = packet contains data
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*/
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#define MAP_PAD_LEN_MASK GENMASK(5, 0)
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#define MAP_CMD_FLAG BIT(7)
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struct rmnet_map_dl_csum_trailer {
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u8 reserved1;
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#if defined(__LITTLE_ENDIAN_BITFIELD)
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u8 valid:1;
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u8 reserved2:7;
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#elif defined (__BIG_ENDIAN_BITFIELD)
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u8 reserved2:7;
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u8 valid:1;
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#else
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#error "Please fix <asm/byteorder.h>"
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#endif
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__be16 csum_start_offset;
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__be16 csum_length;
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__be16 csum_value;
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} __aligned(1);
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struct rmnet_map_ul_csum_header {
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__be16 csum_start_offset;
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#if defined(__LITTLE_ENDIAN_BITFIELD)
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u16 csum_insert_offset:14;
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u16 udp_ind:1;
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u16 csum_enabled:1;
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#elif defined (__BIG_ENDIAN_BITFIELD)
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u16 csum_enabled:1;
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u16 udp_ind:1;
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u16 csum_insert_offset:14;
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#else
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#error "Please fix <asm/byteorder.h>"
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#endif
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} __aligned(1);
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#endif /* !(_LINUX_IF_RMNET_H_) */
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