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/*
 * Common code to handle absent "placeholder" devices
 * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
 * $Id: map_absent.c,v 1.1.1.1 2004-04-15 01:52:07 phoenix Exp $
 *
 * 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/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 = kmalloc(sizeof(*mtd), GFP_KERNEL);
	if (!mtd) {
		return NULL;
	}
 
	memset(mtd, 0, sizeof(*mtd));
 
	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;
 
	MOD_INC_USE_COUNT;
	return mtd;
}
 
 
static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
{
	*retlen = 0;
	return -ENODEV;
}
 
static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
{
	*retlen = 0;
	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 */
}
 
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");