LXR linux/drivers/mtd/chips/map

   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