1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * cb710/sgbuf2.c
4 *
5 * Copyright by Michał Mirosław, 2008-2009
6 */
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/cb710.h>
10
sg_dwiter_next(struct sg_mapping_iter * miter)11 static bool sg_dwiter_next(struct sg_mapping_iter *miter)
12 {
13 if (sg_miter_next(miter)) {
14 miter->consumed = 0;
15 return true;
16 } else
17 return false;
18 }
19
sg_dwiter_is_at_end(struct sg_mapping_iter * miter)20 static bool sg_dwiter_is_at_end(struct sg_mapping_iter *miter)
21 {
22 return miter->length == miter->consumed && !sg_dwiter_next(miter);
23 }
24
sg_dwiter_read_buffer(struct sg_mapping_iter * miter)25 static uint32_t sg_dwiter_read_buffer(struct sg_mapping_iter *miter)
26 {
27 size_t len, left = 4;
28 uint32_t data;
29 void *addr = &data;
30
31 do {
32 len = min(miter->length - miter->consumed, left);
33 memcpy(addr, miter->addr + miter->consumed, len);
34 miter->consumed += len;
35 left -= len;
36 if (!left)
37 return data;
38 addr += len;
39 } while (sg_dwiter_next(miter));
40
41 memset(addr, 0, left);
42 return data;
43 }
44
needs_unaligned_copy(const void * ptr)45 static inline bool needs_unaligned_copy(const void *ptr)
46 {
47 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
48 return false;
49 #else
50 return ((ptr - NULL) & 3) != 0;
51 #endif
52 }
53
sg_dwiter_get_next_block(struct sg_mapping_iter * miter,uint32_t ** ptr)54 static bool sg_dwiter_get_next_block(struct sg_mapping_iter *miter, uint32_t **ptr)
55 {
56 size_t len;
57
58 if (sg_dwiter_is_at_end(miter))
59 return true;
60
61 len = miter->length - miter->consumed;
62
63 if (likely(len >= 4 && !needs_unaligned_copy(
64 miter->addr + miter->consumed))) {
65 *ptr = miter->addr + miter->consumed;
66 miter->consumed += 4;
67 return true;
68 }
69
70 return false;
71 }
72
73 /**
74 * cb710_sg_dwiter_read_next_block() - get next 32-bit word from sg buffer
75 * @miter: sg mapping iterator used for reading
76 *
77 * Description:
78 * Returns 32-bit word starting at byte pointed to by @miter@
79 * handling any alignment issues. Bytes past the buffer's end
80 * are not accessed (read) but are returned as zeroes. @miter@
81 * is advanced by 4 bytes or to the end of buffer whichever is
82 * closer.
83 *
84 * Context:
85 * Same requirements as in sg_miter_next().
86 *
87 * Returns:
88 * 32-bit word just read.
89 */
cb710_sg_dwiter_read_next_block(struct sg_mapping_iter * miter)90 uint32_t cb710_sg_dwiter_read_next_block(struct sg_mapping_iter *miter)
91 {
92 uint32_t *ptr = NULL;
93
94 if (likely(sg_dwiter_get_next_block(miter, &ptr)))
95 return ptr ? *ptr : 0;
96
97 return sg_dwiter_read_buffer(miter);
98 }
99 EXPORT_SYMBOL_GPL(cb710_sg_dwiter_read_next_block);
100
sg_dwiter_write_slow(struct sg_mapping_iter * miter,uint32_t data)101 static void sg_dwiter_write_slow(struct sg_mapping_iter *miter, uint32_t data)
102 {
103 size_t len, left = 4;
104 void *addr = &data;
105
106 do {
107 len = min(miter->length - miter->consumed, left);
108 memcpy(miter->addr, addr, len);
109 miter->consumed += len;
110 left -= len;
111 if (!left)
112 return;
113 addr += len;
114 } while (sg_dwiter_next(miter));
115 }
116
117 /**
118 * cb710_sg_dwiter_write_next_block() - write next 32-bit word to sg buffer
119 * @miter: sg mapping iterator used for writing
120 * @data: data to write to sg buffer
121 *
122 * Description:
123 * Writes 32-bit word starting at byte pointed to by @miter@
124 * handling any alignment issues. Bytes which would be written
125 * past the buffer's end are silently discarded. @miter@ is
126 * advanced by 4 bytes or to the end of buffer whichever is closer.
127 *
128 * Context:
129 * Same requirements as in sg_miter_next().
130 */
cb710_sg_dwiter_write_next_block(struct sg_mapping_iter * miter,uint32_t data)131 void cb710_sg_dwiter_write_next_block(struct sg_mapping_iter *miter, uint32_t data)
132 {
133 uint32_t *ptr = NULL;
134
135 if (likely(sg_dwiter_get_next_block(miter, &ptr))) {
136 if (ptr)
137 *ptr = data;
138 else
139 return;
140 } else
141 sg_dwiter_write_slow(miter, data);
142 }
143 EXPORT_SYMBOL_GPL(cb710_sg_dwiter_write_next_block);
144
145
