1/* 2 * Common code to handle absent "placeholder" devices 3 * Copyright 2001 Resilience Corporation <ebrower@resilience.com> 4 * $Id: map_absent.c,v 1.1.1.1 2007/08/03 18:52:43 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 31static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *); 32static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *); 33static int map_absent_erase (struct mtd_info *, struct erase_info *); 34static void map_absent_sync (struct mtd_info *); 35static struct mtd_info *map_absent_probe(struct map_info *map); 36static void map_absent_destroy (struct mtd_info *); 37 38 39static 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 46static 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 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 100static int __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