linux-old/drivers/mtd/chips/map_absent.c
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   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
  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