1/*
2 * Common code to handle absent "placeholder" devices
3 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
4 * $Id: map_absent.c,v 1.1.1.1 2008/10/15 03:26:35 james26_jang 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
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 = 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
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
100int __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");
117