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linux
1/*
2 * Common code to handle absent "placeholder" devices
3 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
4 * $Id: map_absent.c,v 1.6 2005/11/07 11:14:23 gleixner Exp $
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#include <linux/mtd/compatmac.h>
30
31static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
32static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
33static int map_absent_erase (struct mtd_info *, struct erase_info *);
34static void map_absent_sync (struct mtd_info *);
35static struct mtd_info *map_absent_probe(struct map_info *map);
36static void map_absent_destroy (struct mtd_info *);
37
38
39static struct mtd_chip_driver map_absent_chipdrv = {
40 .probe = map_absent_probe,
41 .destroy = map_absent_destroy,
42 .name = "map_absent",
43 .module = THIS_MODULE
44};
45
46static struct mtd_info *map_absent_probe(struct map_info *map)
47{
48 struct mtd_info *mtd;
49
50 mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
51 if (!mtd) {
52 return NULL;
53 }
54
55 map->fldrv = &map_absent_chipdrv;
56 mtd->priv = map;
57 mtd->name = map->name;
58 mtd->type = MTD_ABSENT;
59 mtd->size = map->size;
60 mtd->erase = map_absent_erase;
61 mtd->read = map_absent_read;
62 mtd->write = map_absent_write;
63 mtd->sync = map_absent_sync;
64 mtd->flags = 0;
65 mtd->erasesize = PAGE_SIZE;
66 mtd->writesize = 1;
67
68 __module_get(THIS_MODULE);
69 return mtd;
70}
71
72
73static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
74{
75 *retlen = 0;
76 return -ENODEV;
77}
78
79static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
80{
81 *retlen = 0;
82 return -ENODEV;
83}
84
85static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
86{
87 return -ENODEV;
88}
89
90static void map_absent_sync(struct mtd_info *mtd)
91{
92 /* nop */
93}
94
95static void map_absent_destroy(struct mtd_info *mtd)
96{
97 /* nop */
98}
99
100static int __init map_absent_init(void)
101{
102 register_mtd_chip_driver(&map_absent_chipdrv);
103 return 0;
104}
105
106static void __exit map_absent_exit(void)
107{
108 unregister_mtd_chip_driver(&map_absent_chipdrv);
109}
110
111module_init(map_absent_init);
112module_exit(map_absent_exit);
113
114MODULE_LICENSE("GPL");
115MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
116MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");