drivers/mtd/chips/map_absent.c

   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
  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         return -ENODEV;
  75 }
  76
  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
  82 static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
  83 {
  84         return -ENODEV;
  85 }
  86
  87 static void map_absent_sync(struct mtd_info *mtd)
  88 {
  89         /* nop */
  90 }
  91
  92 static void map_absent_destroy(struct mtd_info *mtd)
  93 {
  94         /* nop */
  95 }
  96
  97 static int __init map_absent_init(void)
  98 {
  99         register_mtd_chip_driver(&map_absent_chipdrv);
 100         return 0;
 101 }
 102
 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");