map_absent.c revision 834247ec7e281dee839fe4a04bc1bbf0c7395172 
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
29static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
30static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
31static int map_absent_erase (struct mtd_info *, struct erase_info *);
32static void map_absent_sync (struct mtd_info *);
33static struct mtd_info *map_absent_probe(struct map_info *map);
34static void map_absent_destroy (struct mtd_info *);
35
36
37static struct mtd_chip_driver map_absent_chipdrv = {
38	.probe		= map_absent_probe,
39	.destroy	= map_absent_destroy,
40	.name		= "map_absent",
41	.module		= THIS_MODULE
42};
43
44static struct mtd_info *map_absent_probe(struct map_info *map)
45{
46	struct mtd_info *mtd;
47
48	mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
49	if (!mtd) {
50		return NULL;
51	}
52
53	map->fldrv 	= &map_absent_chipdrv;
54	mtd->priv 	= map;
55	mtd->name 	= map->name;
56	mtd->type 	= MTD_ABSENT;
57	mtd->size 	= map->size;
58	mtd->_erase 	= map_absent_erase;
59	mtd->_read 	= map_absent_read;
60	mtd->_write 	= map_absent_write;
61	mtd->_sync 	= map_absent_sync;
62	mtd->flags 	= 0;
63	mtd->erasesize  = PAGE_SIZE;
64	mtd->writesize  = 1;
65
66	__module_get(THIS_MODULE);
67	return mtd;
68}
69
70
71static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
72{
73	return -ENODEV;
74}
75
76static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
77{
78	return -ENODEV;
79}
80
81static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
82{
83	return -ENODEV;
84}
85
86static void map_absent_sync(struct mtd_info *mtd)
87{
88	/* nop */
89}
90
91static void map_absent_destroy(struct mtd_info *mtd)
92{
93	/* nop */
94}
95
96static int __init map_absent_init(void)
97{
98	register_mtd_chip_driver(&map_absent_chipdrv);
99	return 0;
100}
101
102static void __exit map_absent_exit(void)
103{
104	unregister_mtd_chip_driver(&map_absent_chipdrv);
105}
106
107module_init(map_absent_init);
108module_exit(map_absent_exit);
109
110MODULE_LICENSE("GPL");
111MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
112MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");
113