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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Common code to handle absent "placeholder" devices4 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>5 *6 * This map driver is used to allocate "placeholder" MTD7 * devices on systems that have socketed/removable media.8 * Use of this driver as a fallback preserves the expected9 * 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 -ENODEV18 * 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 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_MODULE43};44 45static struct mtd_info *map_absent_probe(struct map_info *map)46{47 struct mtd_info *mtd;48 49 mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);50 if (!mtd) {51 return NULL;52 }53 54 map->fldrv = &map_absent_chipdrv;55 mtd->priv = map;56 mtd->name = map->name;57 mtd->type = MTD_ABSENT;58 mtd->size = map->size;59 mtd->_erase = map_absent_erase;60 mtd->_read = map_absent_read;61 mtd->_write = map_absent_write;62 mtd->_sync = map_absent_sync;63 mtd->flags = 0;64 mtd->erasesize = PAGE_SIZE;65 mtd->writesize = 1;66 67 __module_get(THIS_MODULE);68 return mtd;69}70 71 72static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)73{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 return -ENODEV;80}81 82static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)83{84 return -ENODEV;85}86 87static void map_absent_sync(struct mtd_info *mtd)88{89 /* nop */90}91 92static void map_absent_destroy(struct mtd_info *mtd)93{94 /* nop */95}96 97static int __init map_absent_init(void)98{99 register_mtd_chip_driver(&map_absent_chipdrv);100 return 0;101}102 103static void __exit map_absent_exit(void)104{105 unregister_mtd_chip_driver(&map_absent_chipdrv);106}107 108module_init(map_absent_init);109module_exit(map_absent_exit);110 111MODULE_LICENSE("GPL");112MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");113MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");114