drivers/mtd/chips/map_absent.c

   1 /*
   2  * Common code to handle absent "placeholder" devices
   3  * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
   4  * $Id: map_absent.c,v 1.6 2005/11/07 11:14:23 gleixner 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 #include <linux/init.h>
  27 #include <linux/mtd/mtd.h>
  28 #include <linux/mtd/map.h>
  29 #include <linux/mtd/compatmac.h>
  30
  31 static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
  32 static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
  33 static int map_absent_erase (struct mtd_info *, struct erase_info *);
  34 static void map_absent_sync (struct mtd_info *);
  35 static struct mtd_info *map_absent_probe(struct map_info *map);
  36 static void map_absent_destroy (struct mtd_info *);
  37
  38
  39 static struct mtd_chip_driver map_absent_chipdrv = {
  40         .probe          = map_absent_probe,
  41         .destroy        = map_absent_destroy,
  42         .name           = "map_absent",
  43         .module         = THIS_MODULE
  44 };
  45
  46 static struct mtd_info *map_absent_probe(struct map_info *map)
  47 {
  48         struct mtd_info *mtd;
  49
  50         mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
  51         if (!mtd) {
  52                 return NULL;
  53         }
  54
  55         map->fldrv      = &map_absent_chipdrv;
  56         mtd->priv       = map;
  57         mtd->name       = map->name;
  58         mtd->type       = MTD_ABSENT;
  59         mtd->size       = map->size;
  60         mtd->erase      = map_absent_erase;
  61         mtd->read       = map_absent_read;
  62         mtd->write      = map_absent_write;
  63         mtd->sync       = map_absent_sync;
  64         mtd->flags      = 0;
  65         mtd->erasesize  = PAGE_SIZE;
  66         mtd->writesize  = 1;
  67
  68         __module_get(THIS_MODULE);
  69         return mtd;
  70 }
  71
  72
  73 static 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
  79 static 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
  85 static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
  86 {
  87         return -ENODEV;
  88 }
  89
  90 static void map_absent_sync(struct mtd_info *mtd)
  91 {
  92         /* nop */
  93 }
  94
  95 static void map_absent_destroy(struct mtd_info *mtd)
  96 {
  97         /* nop */
  98 }
  99
 100 static int __init map_absent_init(void)
 101 {
 102         register_mtd_chip_driver(&map_absent_chipdrv);
 103         return 0;
 104 }
 105
 106 static void __exit map_absent_exit(void)
 107 {
 108         unregister_mtd_chip_driver(&map_absent_chipdrv);
 109 }
 110
 111 module_init(map_absent_init);
 112 module_exit(map_absent_exit);
 113
 114 MODULE_LICENSE("GPL");
 115 MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
 116 MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");