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 2008/10/15 03:26:35 james26_jang 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