1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Common code to handle absent "placeholder" devices
4  * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
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 
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 = 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 
map_absent_read(struct mtd_info * mtd,loff_t from,size_t len,size_t * retlen,u_char * buf)72 static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
73 {
74 	return -ENODEV;
75 }
76 
map_absent_write(struct mtd_info * mtd,loff_t to,size_t len,size_t * retlen,const u_char * buf)77 static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
78 {
79 	return -ENODEV;
80 }
81 
map_absent_erase(struct mtd_info * mtd,struct erase_info * instr)82 static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
83 {
84 	return -ENODEV;
85 }
86 
map_absent_sync(struct mtd_info * mtd)87 static void map_absent_sync(struct mtd_info *mtd)
88 {
89 	/* nop */
90 }
91 
map_absent_destroy(struct mtd_info * mtd)92 static void map_absent_destroy(struct mtd_info *mtd)
93 {
94 	/* nop */
95 }
96 
map_absent_init(void)97 static int __init map_absent_init(void)
98 {
99 	register_mtd_chip_driver(&map_absent_chipdrv);
100 	return 0;
101 }
102 
map_absent_exit(void)103 static void __exit map_absent_exit(void)
104 {
105 	unregister_mtd_chip_driver(&map_absent_chipdrv);
106 }
107 
108 module_init(map_absent_init);
109 module_exit(map_absent_exit);
110 
111 MODULE_LICENSE("GPL");
112 MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
113 MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");
114