1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * altera-comp.c
4  *
5  * altera FPGA driver
6  *
7  * Copyright (C) Altera Corporation 1998-2001
8  * Copyright (C) 2010 NetUP Inc.
9  * Copyright (C) 2010 Igor M. Liplianin <liplianin@netup.ru>
10  */
11 
12 #include <linux/kernel.h>
13 #include "altera-exprt.h"
14 
15 #define	SHORT_BITS		16
16 #define	CHAR_BITS		8
17 #define	DATA_BLOB_LENGTH	3
18 #define	MATCH_DATA_LENGTH	8192
19 #define ALTERA_REQUEST_SIZE	1024
20 #define ALTERA_BUFFER_SIZE	(MATCH_DATA_LENGTH + ALTERA_REQUEST_SIZE)
21 
22 static u32 altera_bits_req(u32 n)
23 {
24 	u32 result = SHORT_BITS;
25 
26 	if (n == 0)
27 		result = 1;
28 	else {
29 		/* Look for the highest non-zero bit position */
30 		while ((n & (1 << (SHORT_BITS - 1))) == 0) {
31 			n <<= 1;
32 			--result;
33 		}
34 	}
35 
36 	return result;
37 }
38 
39 static u32 altera_read_packed(u8 *buffer, u32 bits, u32 *bits_avail,
40 							u32 *in_index)
41 {
42 	u32 result = 0;
43 	u32 shift = 0;
44 	u32 databyte = 0;
45 
46 	while (bits > 0) {
47 		databyte = buffer[*in_index];
48 		result |= (((databyte >> (CHAR_BITS - *bits_avail))
49 			& (0xff >> (CHAR_BITS - *bits_avail))) << shift);
50 
51 		if (bits <= *bits_avail) {
52 			result &= (0xffff >> (SHORT_BITS - (bits + shift)));
53 			*bits_avail -= bits;
54 			bits = 0;
55 		} else {
56 			++(*in_index);
57 			shift += *bits_avail;
58 			bits -= *bits_avail;
59 			*bits_avail = CHAR_BITS;
60 		}
61 	}
62 
63 	return result;
64 }
65 
66 u32 altera_shrink(u8 *in, u32 in_length, u8 *out, u32 out_length, s32 version)
67 {
68 	u32 i, j, data_length = 0L;
69 	u32 offset, length;
70 	u32 match_data_length = MATCH_DATA_LENGTH;
71 	u32 bits_avail = CHAR_BITS;
72 	u32 in_index = 0L;
73 
74 	if (version > 0)
75 		--match_data_length;
76 
77 	for (i = 0; i < out_length; ++i)
78 		out[i] = 0;
79 
80 	/* Read number of bytes in data. */
81 	for (i = 0; i < sizeof(in_length); ++i) {
82 		data_length = data_length | (
83 			altera_read_packed(in,
84 					CHAR_BITS,
85 					&bits_avail,
86 					&in_index) << (i * CHAR_BITS));
87 	}
88 
89 	if (data_length > out_length) {
90 		data_length = 0L;
91 		return data_length;
92 	}
93 
94 	i = 0;
95 	while (i < data_length) {
96 		/* A 0 bit indicates literal data. */
97 		if (altera_read_packed(in, 1, &bits_avail,
98 						&in_index) == 0) {
99 			for (j = 0; j < DATA_BLOB_LENGTH; ++j) {
100 				if (i < data_length) {
101 					out[i] = (u8)altera_read_packed(in,
102 							CHAR_BITS,
103 							&bits_avail,
104 							&in_index);
105 					i++;
106 				}
107 			}
108 		} else {
109 			/* A 1 bit indicates offset/length to follow. */
110 			offset = altera_read_packed(in, altera_bits_req((s16)
111 					(i > match_data_length ?
112 						match_data_length : i)),
113 					&bits_avail,
114 					&in_index);
115 			length = altera_read_packed(in, CHAR_BITS,
116 					&bits_avail,
117 					&in_index);
118 			for (j = 0; j < length; ++j) {
119 				if (i < data_length) {
120 					out[i] = out[i - offset];
121 					i++;
122 				}
123 			}
124 		}
125 	}
126 
127 	return data_length;
128 }
129