drivers/mtd/chips/map_absent.c

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