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 *retlen = 0; 74 return -ENODEV; 75} 76 77static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf) 78{ 79 *retlen = 0; 80 return -ENODEV; 81} 82 83static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr) 84{ 85 return -ENODEV; 86} 87 88static void map_absent_sync(struct mtd_info *mtd) 89{ 90 /* nop */ 91} 92 93static void map_absent_destroy(struct mtd_info *mtd) 94{ 95 /* nop */ 96} 97 98static int __init map_absent_init(void) 99{ 100 register_mtd_chip_driver(&map_absent_chipdrv); 101 return 0; 102} 103 104static void __exit map_absent_exit(void) 105{ 106 unregister_mtd_chip_driver(&map_absent_chipdrv); 107} 108 109module_init(map_absent_init); 110module_exit(map_absent_exit); 111 112MODULE_LICENSE("GPL"); 113MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>"); 114MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips"); 115