map_absent.c

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/*
 * Common code to handle absent "placeholder" devices
 * Copyright 2001 Resilience Corporation <[email protected]>
 *
 * 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 <[email protected]>");
MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");