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1/* SPDX-License-Identifier: GPL-2.0 */2 3#ifndef __842_H__4#define __842_H__5 6/* The 842 compressed format is made up of multiple blocks, each of7 * which have the format:8 *9 * <template>[arg1][arg2][arg3][arg4]10 *11 * where there are between 0 and 4 template args, depending on the specific12 * template operation. For normal operations, each arg is either a specific13 * number of data bytes to add to the output buffer, or an index pointing14 * to a previously-written number of data bytes to copy to the output buffer.15 *16 * The template code is a 5-bit value. This code indicates what to do with17 * the following data. Template codes from 0 to 0x19 should use the template18 * table, the static "decomp_ops" table used in decompress. For each template19 * (table row), there are between 1 and 4 actions; each action corresponds to20 * an arg following the template code bits. Each action is either a "data"21 * type action, or a "index" type action, and each action results in 2, 4, or 822 * bytes being written to the output buffer. Each template (i.e. all actions23 * in the table row) will add up to 8 bytes being written to the output buffer.24 * Any row with less than 4 actions is padded with noop actions, indicated by25 * N0 (for which there is no corresponding arg in the compressed data buffer).26 *27 * "Data" actions, indicated in the table by D2, D4, and D8, mean that the28 * corresponding arg is 2, 4, or 8 bytes, respectively, in the compressed data29 * buffer should be copied directly to the output buffer.30 *31 * "Index" actions, indicated in the table by I2, I4, and I8, mean the32 * corresponding arg is an index parameter that points to, respectively, a 2,33 * 4, or 8 byte value already in the output buffer, that should be copied to34 * the end of the output buffer. Essentially, the index points to a position35 * in a ring buffer that contains the last N bytes of output buffer data.36 * The number of bits for each index's arg are: 8 bits for I2, 9 bits for I4,37 * and 8 bits for I8. Since each index points to a 2, 4, or 8 byte section,38 * this means that I2 can reference 512 bytes ((2^8 bits = 256) * 2 bytes), I439 * can reference 2048 bytes ((2^9 = 512) * 4 bytes), and I8 can reference 204840 * bytes ((2^8 = 256) * 8 bytes). Think of it as a kind-of ring buffer for41 * each of I2, I4, and I8 that are updated for each byte written to the output42 * buffer. In this implementation, the output buffer is directly used for each43 * index; there is no additional memory required. Note that the index is into44 * a ring buffer, not a sliding window; for example, if there have been 26045 * bytes written to the output buffer, an I2 index of 0 would index to byte 25646 * in the output buffer, while an I2 index of 16 would index to byte 16 in the47 * output buffer.48 *49 * There are also 3 special template codes; 0x1b for "repeat", 0x1c for50 * "zeros", and 0x1e for "end". The "repeat" operation is followed by a 6 bit51 * arg N indicating how many times to repeat. The last 8 bytes written to the52 * output buffer are written again to the output buffer, N + 1 times. The53 * "zeros" operation, which has no arg bits, writes 8 zeros to the output54 * buffer. The "end" operation, which also has no arg bits, signals the end55 * of the compressed data. There may be some number of padding (don't care,56 * but usually 0) bits after the "end" operation bits, to fill the buffer57 * length to a specific byte multiple (usually a multiple of 8, 16, or 3258 * bytes).59 *60 * This software implementation also uses one of the undefined template values,61 * 0x1d as a special "short data" template code, to represent less than 8 bytes62 * of uncompressed data. It is followed by a 3 bit arg N indicating how many63 * data bytes will follow, and then N bytes of data, which should be copied to64 * the output buffer. This allows the software 842 compressor to accept input65 * buffers that are not an exact multiple of 8 bytes long. However, those66 * compressed buffers containing this sw-only template will be rejected by67 * the 842 hardware decompressor, and must be decompressed with this software68 * library. The 842 software compression module includes a parameter to69 * disable using this sw-only "short data" template, and instead simply70 * reject any input buffer that is not a multiple of 8 bytes long.71 *72 * After all actions for each operation code are processed, another template73 * code is in the next 5 bits. The decompression ends once the "end" template74 * code is detected.75 */76 77#include <linux/module.h>78#include <linux/kernel.h>79#include <linux/bitops.h>80#include <linux/crc32.h>81#include <linux/unaligned.h>82 83#include <linux/sw842.h>84 85/* special templates */86#define OP_REPEAT (0x1B)87#define OP_ZEROS (0x1C)88#define OP_END (0x1E)89 90/* sw only template - this is not in the hw design; it's used only by this91 * software compressor and decompressor, to allow input buffers that aren't92 * a multiple of 8.93 */94#define OP_SHORT_DATA (0x1D)95 96/* additional bits of each op param */97#define OP_BITS (5)98#define REPEAT_BITS (6)99#define SHORT_DATA_BITS (3)100#define I2_BITS (8)101#define I4_BITS (9)102#define I8_BITS (8)103#define CRC_BITS (32)104 105#define REPEAT_BITS_MAX (0x3f)106#define SHORT_DATA_BITS_MAX (0x7)107 108/* Arbitrary values used to indicate action */109#define OP_ACTION (0x70)110#define OP_ACTION_INDEX (0x10)111#define OP_ACTION_DATA (0x20)112#define OP_ACTION_NOOP (0x40)113#define OP_AMOUNT (0x0f)114#define OP_AMOUNT_0 (0x00)115#define OP_AMOUNT_2 (0x02)116#define OP_AMOUNT_4 (0x04)117#define OP_AMOUNT_8 (0x08)118 119#define D2 (OP_ACTION_DATA | OP_AMOUNT_2)120#define D4 (OP_ACTION_DATA | OP_AMOUNT_4)121#define D8 (OP_ACTION_DATA | OP_AMOUNT_8)122#define I2 (OP_ACTION_INDEX | OP_AMOUNT_2)123#define I4 (OP_ACTION_INDEX | OP_AMOUNT_4)124#define I8 (OP_ACTION_INDEX | OP_AMOUNT_8)125#define N0 (OP_ACTION_NOOP | OP_AMOUNT_0)126 127/* the max of the regular templates - not including the special templates */128#define OPS_MAX (0x1a)129 130#endif131