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linux
1/*
2 * Common code to handle absent "placeholder" devices
3 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
4 *
5 * This map driver is used to allocate "placeholder" MTD
6 * devices on systems that have socketed/removable media.
7 * Use of this driver as a fallback preserves the expected
8 * registration of MTD device nodes regardless of probe outcome.
9 * A usage example is as follows:
10 *
11 * my_dev[i] = do_map_probe("cfi", &my_map[i]);
12 * if(NULL == my_dev[i]) {
13 * my_dev[i] = do_map_probe("map_absent", &my_map[i]);
14 * }
15 *
16 * Any device 'probed' with this driver will return -ENODEV
17 * upon open.
18 */
19
20#include <linux/module.h>
21#include <linux/types.h>
22#include <linux/kernel.h>
23#include <linux/errno.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/mtd/mtd.h>
27#include <linux/mtd/map.h>
28#include <linux/mtd/compatmac.h>
29
30static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
31static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
32static int map_absent_erase (struct mtd_info *, struct erase_info *);
33static void map_absent_sync (struct mtd_info *);
34static struct mtd_info *map_absent_probe(struct map_info *map);
35static void map_absent_destroy (struct mtd_info *);
36
37
38static 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
45static struct mtd_info *map_absent_probe(struct map_info *map)
46{
47 struct mtd_info *mtd;
48
49 mtd = kzalloc(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
72static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
73{
74 *retlen = 0;
75 return -ENODEV;
76}
77
78static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
79{
80 *retlen = 0;
81 return -ENODEV;
82}
83
84static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
85{
86 return -ENODEV;
87}
88
89static void map_absent_sync(struct mtd_info *mtd)
90{
91 /* nop */
92}
93
94static void map_absent_destroy(struct mtd_info *mtd)
95{
96 /* nop */
97}
98
99static int __init map_absent_init(void)
100{
101 register_mtd_chip_driver(&map_absent_chipdrv);
102 return 0;
103}
104
105static void __exit map_absent_exit(void)
106{
107 unregister_mtd_chip_driver(&map_absent_chipdrv);
108}
109
110module_init(map_absent_init);
111module_exit(map_absent_exit);
112
113MODULE_LICENSE("GPL");
114MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
115MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");