1 /*
2 * Common code to handle absent "placeholder" devices
3 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
4 * $Id: map_absent.c,v 1.2 2001/10/02 15:05:12 dwmw2 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
27 #include <linux/mtd/map.h>
28
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
map_absent_probe(struct map_info * map)45 static struct mtd_info *map_absent_probe(struct map_info *map)
46 {
47 struct mtd_info *mtd;
48
49 mtd = kmalloc(sizeof(*mtd), GFP_KERNEL);
50 if (!mtd) {
51 return NULL;
52 }
53
54 memset(mtd, 0, sizeof(*mtd));
55
56 map->fldrv = &map_absent_chipdrv;
57 mtd->priv = map;
58 mtd->name = map->name;
59 mtd->type = MTD_ABSENT;
60 mtd->size = map->size;
61 mtd->erase = map_absent_erase;
62 mtd->read = map_absent_read;
63 mtd->write = map_absent_write;
64 mtd->sync = map_absent_sync;
65 mtd->flags = 0;
66 mtd->erasesize = PAGE_SIZE;
67
68 MOD_INC_USE_COUNT;
69 return mtd;
70 }
71
72
map_absent_read(struct mtd_info * mtd,loff_t from,size_t len,size_t * retlen,u_char * buf)73 static 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
map_absent_write(struct mtd_info * mtd,loff_t to,size_t len,size_t * retlen,const u_char * buf)79 static 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
map_absent_erase(struct mtd_info * mtd,struct erase_info * instr)85 static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
86 {
87 return -ENODEV;
88 }
89
map_absent_sync(struct mtd_info * mtd)90 static void map_absent_sync(struct mtd_info *mtd)
91 {
92 /* nop */
93 }
94
map_absent_destroy(struct mtd_info * mtd)95 static void map_absent_destroy(struct mtd_info *mtd)
96 {
97 /* nop */
98 }
99
map_absent_init(void)100 int __init map_absent_init(void)
101 {
102 register_mtd_chip_driver(&map_absent_chipdrv);
103 return 0;
104 }
105
map_absent_exit(void)106 static void __exit map_absent_exit(void)
107 {
108 unregister_mtd_chip_driver(&map_absent_chipdrv);
109 }
110
111 module_init(map_absent_init);
112 module_exit(map_absent_exit);
113
114 MODULE_LICENSE("GPL");
115 MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
116 MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");
117