Re: [RFC PATCH 09/16] soundwire: crc8: add constant table

[Vinod Koul <vkoul@xxxxxxxxxx>]

On 07-12-23, 16:29, Pierre-Louis Bossart wrote:
> Add the lookup table required by crc8(). All configuration values were
> directly table from the MIPI SoundWire 1.x specification.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
>  drivers/soundwire/Makefile |   4 +-
>  drivers/soundwire/crc8.c   | 277 +++++++++++++++++++++++++++++++++++++
>  drivers/soundwire/crc8.h   |  11 ++
>  3 files changed, 291 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/soundwire/crc8.c
>  create mode 100644 drivers/soundwire/crc8.h
> 
> diff --git a/drivers/soundwire/Makefile b/drivers/soundwire/Makefile
> index 657f5888a77b..170128dd9318 100644
> --- a/drivers/soundwire/Makefile
> +++ b/drivers/soundwire/Makefile
> @@ -5,7 +5,9 @@
>  
>  #Bus Objs
>  soundwire-bus-y := bus_type.o bus.o master.o slave.o mipi_disco.o stream.o  \
> -			sysfs_slave.o sysfs_slave_dpn.o
> +			sysfs_slave.o sysfs_slave_dpn.o \
> +			crc8.o
> +
>  obj-$(CONFIG_SOUNDWIRE) += soundwire-bus.o
>  
>  soundwire-generic-allocation-objs := generic_bandwidth_allocation.o
> diff --git a/drivers/soundwire/crc8.c b/drivers/soundwire/crc8.c
> new file mode 100644
> index 000000000000..b6b984d7f39a
> --- /dev/null
> +++ b/drivers/soundwire/crc8.c
> @@ -0,0 +1,277 @@
> +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> +// Copyright(c) 2024 Intel Corporation.
> +
> +#include <linux/crc8.h>
> +#include <linux/module.h>
> +#include "crc8.h"
> +
> +/*
> + * the MIPI SoundWire CRC8 polynomial is X^8 + X^6 + X^3 + X^2 + 1, MSB first
> + * The value is (1)01001101 = 0x4D
> + *
> + * the table below was generated with
> + *
> + *	u8 crc8_lookup_table[CRC8_TABLE_SIZE];
> + *	crc8_populate_msb(crc8_lookup_table, SDW_CRC8_POLY);

Good that you found this API, so next question would be why should we
have this static table in kernel and not generate on probe if bpt is
supported..? Many subsystems use these APIs to generate the tables..


> + *
> + */
> +
> +const u8 sdw_crc8_lookup_msb[CRC8_TABLE_SIZE] = {
> +	0x00, /* 0 */
> +	0x4d, /* 1 */
> +	0x9a, /* 2 */
> +	0xd7, /* 3 */
> +	0x79, /* 4 */
> +	0x34, /* 5 */
> +	0xe3, /* 6 */
> +	0xae, /* 7 */
> +	0xf2, /* 8 */
> +	0xbf, /* 9 */
> +	0x68, /* 10 */
> +	0x25, /* 11 */
> +	0x8b, /* 12 */
> +	0xc6, /* 13 */
> +	0x11, /* 14 */
> +	0x5c, /* 15 */
> +	0xa9, /* 16 */
> +	0xe4, /* 17 */
> +	0x33, /* 18 */
> +	0x7e, /* 19 */
> +	0xd0, /* 20 */
> +	0x9d, /* 21 */
> +	0x4a, /* 22 */
> +	0x07, /* 23 */
> +	0x5b, /* 24 */
> +	0x16, /* 25 */
> +	0xc1, /* 26 */
> +	0x8c, /* 27 */
> +	0x22, /* 28 */
> +	0x6f, /* 29 */
> +	0xb8, /* 30 */
> +	0xf5, /* 31 */
> +	0x1f, /* 32 */
> +	0x52, /* 33 */
> +	0x85, /* 34 */
> +	0xc8, /* 35 */
> +	0x66, /* 36 */
> +	0x2b, /* 37 */
> +	0xfc, /* 38 */
> +	0xb1, /* 39 */
> +	0xed, /* 40 */
> +	0xa0, /* 41 */
> +	0x77, /* 42 */
> +	0x3a, /* 43 */
> +	0x94, /* 44 */
> +	0xd9, /* 45 */
> +	0x0e, /* 46 */
> +	0x43, /* 47 */
> +	0xb6, /* 48 */
> +	0xfb, /* 49 */
> +	0x2c, /* 50 */
> +	0x61, /* 51 */
> +	0xcf, /* 52 */
> +	0x82, /* 53 */
> +	0x55, /* 54 */
> +	0x18, /* 55 */
> +	0x44, /* 56 */
> +	0x09, /* 57 */
> +	0xde, /* 58 */
> +	0x93, /* 59 */
> +	0x3d, /* 60 */
> +	0x70, /* 61 */
> +	0xa7, /* 62 */
> +	0xea, /* 63 */
> +	0x3e, /* 64 */
> +	0x73, /* 65 */
> +	0xa4, /* 66 */
> +	0xe9, /* 67 */
> +	0x47, /* 68 */
> +	0x0a, /* 69 */
> +	0xdd, /* 70 */
> +	0x90, /* 71 */
> +	0xcc, /* 72 */
> +	0x81, /* 73 */
> +	0x56, /* 74 */
> +	0x1b, /* 75 */
> +	0xb5, /* 76 */
> +	0xf8, /* 77 */
> +	0x2f, /* 78 */
> +	0x62, /* 79 */
> +	0x97, /* 80 */
> +	0xda, /* 81 */
> +	0x0d, /* 82 */
> +	0x40, /* 83 */
> +	0xee, /* 84 */
> +	0xa3, /* 85 */
> +	0x74, /* 86 */
> +	0x39, /* 87 */
> +	0x65, /* 88 */
> +	0x28, /* 89 */
> +	0xff, /* 90 */
> +	0xb2, /* 91 */
> +	0x1c, /* 92 */
> +	0x51, /* 93 */
> +	0x86, /* 94 */
> +	0xcb, /* 95 */
> +	0x21, /* 96 */
> +	0x6c, /* 97 */
> +	0xbb, /* 98 */
> +	0xf6, /* 99 */
> +	0x58, /* 100 */
> +	0x15, /* 101 */
> +	0xc2, /* 102 */
> +	0x8f, /* 103 */
> +	0xd3, /* 104 */
> +	0x9e, /* 105 */
> +	0x49, /* 106 */
> +	0x04, /* 107 */
> +	0xaa, /* 108 */
> +	0xe7, /* 109 */
> +	0x30, /* 110 */
> +	0x7d, /* 111 */
> +	0x88, /* 112 */
> +	0xc5, /* 113 */
> +	0x12, /* 114 */
> +	0x5f, /* 115 */
> +	0xf1, /* 116 */
> +	0xbc, /* 117 */
> +	0x6b, /* 118 */
> +	0x26, /* 119 */
> +	0x7a, /* 120 */
> +	0x37, /* 121 */
> +	0xe0, /* 122 */
> +	0xad, /* 123 */
> +	0x03, /* 124 */
> +	0x4e, /* 125 */
> +	0x99, /* 126 */
> +	0xd4, /* 127 */
> +	0x7c, /* 128 */
> +	0x31, /* 129 */
> +	0xe6, /* 130 */
> +	0xab, /* 131 */
> +	0x05, /* 132 */
> +	0x48, /* 133 */
> +	0x9f, /* 134 */
> +	0xd2, /* 135 */
> +	0x8e, /* 136 */
> +	0xc3, /* 137 */
> +	0x14, /* 138 */
> +	0x59, /* 139 */
> +	0xf7, /* 140 */
> +	0xba, /* 141 */
> +	0x6d, /* 142 */
> +	0x20, /* 143 */
> +	0xd5, /* 144 */
> +	0x98, /* 145 */
> +	0x4f, /* 146 */
> +	0x02, /* 147 */
> +	0xac, /* 148 */
> +	0xe1, /* 149 */
> +	0x36, /* 150 */
> +	0x7b, /* 151 */
> +	0x27, /* 152 */
> +	0x6a, /* 153 */
> +	0xbd, /* 154 */
> +	0xf0, /* 155 */
> +	0x5e, /* 156 */
> +	0x13, /* 157 */
> +	0xc4, /* 158 */
> +	0x89, /* 159 */
> +	0x63, /* 160 */
> +	0x2e, /* 161 */
> +	0xf9, /* 162 */
> +	0xb4, /* 163 */
> +	0x1a, /* 164 */
> +	0x57, /* 165 */
> +	0x80, /* 166 */
> +	0xcd, /* 167 */
> +	0x91, /* 168 */
> +	0xdc, /* 169 */
> +	0x0b, /* 170 */
> +	0x46, /* 171 */
> +	0xe8, /* 172 */
> +	0xa5, /* 173 */
> +	0x72, /* 174 */
> +	0x3f, /* 175 */
> +	0xca, /* 176 */
> +	0x87, /* 177 */
> +	0x50, /* 178 */
> +	0x1d, /* 179 */
> +	0xb3, /* 180 */
> +	0xfe, /* 181 */
> +	0x29, /* 182 */
> +	0x64, /* 183 */
> +	0x38, /* 184 */
> +	0x75, /* 185 */
> +	0xa2, /* 186 */
> +	0xef, /* 187 */
> +	0x41, /* 188 */
> +	0x0c, /* 189 */
> +	0xdb, /* 190 */
> +	0x96, /* 191 */
> +	0x42, /* 192 */
> +	0x0f, /* 193 */
> +	0xd8, /* 194 */
> +	0x95, /* 195 */
> +	0x3b, /* 196 */
> +	0x76, /* 197 */
> +	0xa1, /* 198 */
> +	0xec, /* 199 */
> +	0xb0, /* 200 */
> +	0xfd, /* 201 */
> +	0x2a, /* 202 */
> +	0x67, /* 203 */
> +	0xc9, /* 204 */
> +	0x84, /* 205 */
> +	0x53, /* 206 */
> +	0x1e, /* 207 */
> +	0xeb, /* 208 */
> +	0xa6, /* 209 */
> +	0x71, /* 210 */
> +	0x3c, /* 211 */
> +	0x92, /* 212 */
> +	0xdf, /* 213 */
> +	0x08, /* 214 */
> +	0x45, /* 215 */
> +	0x19, /* 216 */
> +	0x54, /* 217 */
> +	0x83, /* 218 */
> +	0xce, /* 219 */
> +	0x60, /* 220 */
> +	0x2d, /* 221 */
> +	0xfa, /* 222 */
> +	0xb7, /* 223 */
> +	0x5d, /* 224 */
> +	0x10, /* 225 */
> +	0xc7, /* 226 */
> +	0x8a, /* 227 */
> +	0x24, /* 228 */
> +	0x69, /* 229 */
> +	0xbe, /* 230 */
> +	0xf3, /* 231 */
> +	0xaf, /* 232 */
> +	0xe2, /* 233 */
> +	0x35, /* 234 */
> +	0x78, /* 235 */
> +	0xd6, /* 236 */
> +	0x9b, /* 237 */
> +	0x4c, /* 238 */
> +	0x01, /* 239 */
> +	0xf4, /* 240 */
> +	0xb9, /* 241 */
> +	0x6e, /* 242 */
> +	0x23, /* 243 */
> +	0x8d, /* 244 */
> +	0xc0, /* 245 */
> +	0x17, /* 246 */
> +	0x5a, /* 247 */
> +	0x06, /* 248 */
> +	0x4b, /* 249 */
> +	0x9c, /* 250 */
> +	0xd1, /* 251 */
> +	0x7f, /* 252 */
> +	0x32, /* 253 */
> +	0xe5, /* 254 */
> +	0xa8  /* 255 */
> +};
> +EXPORT_SYMBOL(sdw_crc8_lookup_msb);
> diff --git a/drivers/soundwire/crc8.h b/drivers/soundwire/crc8.h
> new file mode 100644
> index 000000000000..9a88d3866016
> --- /dev/null
> +++ b/drivers/soundwire/crc8.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
> +/* Copyright(c) 2024 Intel Corporation. */
> +
> +#ifndef __SDW_CRC8_H
> +#define __SDW_CRC8_H
> +
> +#define SDW_CRC8_SEED 0xFF
> +#define SDW_CRC8_POLY 0x4D
> +extern const u8 sdw_crc8_lookup_msb[CRC8_TABLE_SIZE];
> +
> +#endif /* __SDW_CRC8_H */
> -- 
> 2.39.2
> 

-- 
~Vinod