cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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map_absent.c (2912B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Common code to handle absent "placeholder" devices
      4 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
      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
     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 = 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");