1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Common code to handle absent "placeholder" devices |
4 | * Copyright 2001 Resilience Corporation <ebrower@resilience.com> |
5 | * |
6 | * This map driver is used to allocate "placeholder" MTD |
7 | * devices on systems that have socketed/removable media. |
8 | * Use of this driver as a fallback preserves the expected |
9 | * registration of MTD device nodes regardless of probe outcome. |
10 | * A usage example is as follows: |
11 | * |
12 | * my_dev[i] = do_map_probe("cfi", &my_map[i]); |
13 | * if(NULL == my_dev[i]) { |
14 | * my_dev[i] = do_map_probe("map_absent", &my_map[i]); |
15 | * } |
16 | * |
17 | * Any device 'probed' with this driver will return -ENODEV |
18 | * upon open. |
19 | */ |
20 | |
21 | #include <linux/module.h> |
22 | #include <linux/types.h> |
23 | #include <linux/kernel.h> |
24 | #include <linux/errno.h> |
25 | #include <linux/slab.h> |
26 | #include <linux/init.h> |
27 | #include <linux/mtd/mtd.h> |
28 | #include <linux/mtd/map.h> |
29 | |
30 | static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *); |
31 | static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *); |
32 | static int map_absent_erase (struct mtd_info *, struct erase_info *); |
33 | static void map_absent_sync (struct mtd_info *); |
34 | static struct mtd_info *map_absent_probe(struct map_info *map); |
35 | static void map_absent_destroy (struct mtd_info *); |
36 | |
37 | |
38 | static struct mtd_chip_driver map_absent_chipdrv = { |
39 | .probe = map_absent_probe, |
40 | .destroy = map_absent_destroy, |
41 | .name = "map_absent" , |
42 | .module = THIS_MODULE |
43 | }; |
44 | |
45 | static struct mtd_info *map_absent_probe(struct map_info *map) |
46 | { |
47 | struct mtd_info *mtd; |
48 | |
49 | mtd = kzalloc(size: sizeof(*mtd), GFP_KERNEL); |
50 | if (!mtd) { |
51 | return NULL; |
52 | } |
53 | |
54 | map->fldrv = &map_absent_chipdrv; |
55 | mtd->priv = map; |
56 | mtd->name = map->name; |
57 | mtd->type = MTD_ABSENT; |
58 | mtd->size = map->size; |
59 | mtd->_erase = map_absent_erase; |
60 | mtd->_read = map_absent_read; |
61 | mtd->_write = map_absent_write; |
62 | mtd->_sync = map_absent_sync; |
63 | mtd->flags = 0; |
64 | mtd->erasesize = PAGE_SIZE; |
65 | mtd->writesize = 1; |
66 | |
67 | __module_get(THIS_MODULE); |
68 | return mtd; |
69 | } |
70 | |
71 | |
72 | static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) |
73 | { |
74 | return -ENODEV; |
75 | } |
76 | |
77 | static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf) |
78 | { |
79 | return -ENODEV; |
80 | } |
81 | |
82 | static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr) |
83 | { |
84 | return -ENODEV; |
85 | } |
86 | |
87 | static void map_absent_sync(struct mtd_info *mtd) |
88 | { |
89 | /* nop */ |
90 | } |
91 | |
92 | static void map_absent_destroy(struct mtd_info *mtd) |
93 | { |
94 | /* nop */ |
95 | } |
96 | |
97 | static int __init map_absent_init(void) |
98 | { |
99 | register_mtd_chip_driver(&map_absent_chipdrv); |
100 | return 0; |
101 | } |
102 | |
103 | static void __exit map_absent_exit(void) |
104 | { |
105 | unregister_mtd_chip_driver(&map_absent_chipdrv); |
106 | } |
107 | |
108 | module_init(map_absent_init); |
109 | module_exit(map_absent_exit); |
110 | |
111 | MODULE_LICENSE("GPL" ); |
112 | MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>" ); |
113 | MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips" ); |
114 | |