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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 | // SPDX-License-Identifier: GPL-2.0-only /* * Common code to handle absent "placeholder" devices * Copyright 2001 Resilience Corporation <ebrower@resilience.com> * * This map driver is used to allocate "placeholder" MTD * devices on systems that have socketed/removable media. * Use of this driver as a fallback preserves the expected * registration of MTD device nodes regardless of probe outcome. * A usage example is as follows: * * my_dev[i] = do_map_probe("cfi", &my_map[i]); * if(NULL == my_dev[i]) { * my_dev[i] = do_map_probe("map_absent", &my_map[i]); * } * * Any device 'probed' with this driver will return -ENODEV * upon open. */ #include <linux/module.h> #include <linux/types.h> #include <linux/kernel.h> #include <linux/errno.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/mtd/mtd.h> #include <linux/mtd/map.h> static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *); static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *); static int map_absent_erase (struct mtd_info *, struct erase_info *); static void map_absent_sync (struct mtd_info *); static struct mtd_info *map_absent_probe(struct map_info *map); static void map_absent_destroy (struct mtd_info *); static struct mtd_chip_driver map_absent_chipdrv = { .probe = map_absent_probe, .destroy = map_absent_destroy, .name = "map_absent", .module = THIS_MODULE }; static struct mtd_info *map_absent_probe(struct map_info *map) { struct mtd_info *mtd; mtd = kzalloc(sizeof(*mtd), GFP_KERNEL); if (!mtd) { return NULL; } map->fldrv = &map_absent_chipdrv; mtd->priv = map; mtd->name = map->name; mtd->type = MTD_ABSENT; mtd->size = map->size; mtd->_erase = map_absent_erase; mtd->_read = map_absent_read; mtd->_write = map_absent_write; mtd->_sync = map_absent_sync; mtd->flags = 0; mtd->erasesize = PAGE_SIZE; mtd->writesize = 1; __module_get(THIS_MODULE); return mtd; } static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) { return -ENODEV; } static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf) { return -ENODEV; } static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr) { return -ENODEV; } static void map_absent_sync(struct mtd_info *mtd) { /* nop */ } static void map_absent_destroy(struct mtd_info *mtd) { /* nop */ } static int __init map_absent_init(void) { register_mtd_chip_driver(&map_absent_chipdrv); return 0; } static void __exit map_absent_exit(void) { unregister_mtd_chip_driver(&map_absent_chipdrv); } module_init(map_absent_init); module_exit(map_absent_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>"); MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips"); |