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 = kmalloc(sizeof(*mtd), GFP_KERNEL); 51 if (!mtd) { 52 return NULL; 53 } 54 55 memset(mtd, 0, sizeof(*mtd)); 56 57 map->fldrv = &map_absent_chipdrv; 58 mtd->priv = map; 59 mtd->name = map->name; 60 mtd->type = MTD_ABSENT; 61 mtd->size = map->size; 62 mtd->erase = map_absent_erase; 63 mtd->read = map_absent_read; 64 mtd->write = map_absent_write; 65 mtd->sync = map_absent_sync; 66 mtd->flags = 0; 67 mtd->erasesize = PAGE_SIZE; 68 mtd->writesize = 1; 69 70 __module_get(THIS_MODULE); 71 return mtd; 72 } 73 74 75 static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) 76 { 77 *retlen = 0; 78 return -ENODEV; 79 } 80 81 static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf) 82 { 83 *retlen = 0; 84 return -ENODEV; 85 } 86 87 static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr) 88 { 89 return -ENODEV; 90 } 91 92 static void map_absent_sync(struct mtd_info *mtd) 93 { 94 /* nop */ 95 } 96 97 static void map_absent_destroy(struct mtd_info *mtd) 98 { 99 /* nop */ 100 } 101 102 static int __init map_absent_init(void) 103 { 104 register_mtd_chip_driver(&map_absent_chipdrv); 105 return 0; 106 } 107 108 static void __exit map_absent_exit(void) 109 { 110 unregister_mtd_chip_driver(&map_absent_chipdrv); 111 } 112 113 module_init(map_absent_init); 114 module_exit(map_absent_exit); 115 116 MODULE_LICENSE("GPL"); 117 MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>"); 118 MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips"); 119