map_ram.c

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/*
 * Common code to handle map devices which are simple RAM
 * (C) 2000 Red Hat. GPL'd.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/io.h>
#include <asm/byteorder.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 mapram_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
static int mapram_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
static int mapram_erase (struct mtd_info *, struct erase_info *);
static void mapram_nop (struct mtd_info *);
static struct mtd_info *map_ram_probe(struct map_info *map);
static unsigned long mapram_unmapped_area(struct mtd_info *, unsigned long,
                      unsigned long, unsigned long);


static struct mtd_chip_driver mapram_chipdrv = {
    .probe  = map_ram_probe,
    .name   = "map_ram",
    .module = THIS_MODULE
};

static struct mtd_info *map_ram_probe(struct map_info *map)
{
    struct mtd_info *mtd;

    /* Check the first byte is RAM */
#if 0
    map_write8(map, 0x55, 0);
    if (map_read8(map, 0) != 0x55)
        return NULL;

    map_write8(map, 0xAA, 0);
    if (map_read8(map, 0) != 0xAA)
        return NULL;

    /* Check the last byte is RAM */
    map_write8(map, 0x55, map->size-1);
    if (map_read8(map, map->size-1) != 0x55)
        return NULL;

    map_write8(map, 0xAA, map->size-1);
    if (map_read8(map, map->size-1) != 0xAA)
        return NULL;
#endif
    /* OK. It seems to be RAM. */

    mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
    if (!mtd)
        return NULL;

    map->fldrv = &mapram_chipdrv;
    mtd->priv = map;
    mtd->name = map->name;
    mtd->type = MTD_RAM;
    mtd->size = map->size;
    mtd->_erase = mapram_erase;
    mtd->_get_unmapped_area = mapram_unmapped_area;
    mtd->_read = mapram_read;
    mtd->_write = mapram_write;
    mtd->_sync = mapram_nop;
    mtd->flags = MTD_CAP_RAM;
    mtd->writesize = 1;

    mtd->erasesize = PAGE_SIZE;
    while(mtd->size & (mtd->erasesize - 1))
        mtd->erasesize >>= 1;

    __module_get(THIS_MODULE);
    return mtd;
}


/*
 * Allow NOMMU mmap() to directly map the device (if not NULL)
 * - return the address to which the offset maps
 * - return -ENOSYS to indicate refusal to do the mapping
 */
static unsigned long mapram_unmapped_area(struct mtd_info *mtd,
                      unsigned long len,
                      unsigned long offset,
                      unsigned long flags)
{
    struct map_info *map = mtd->priv;
    return (unsigned long) map->virt + offset;
}

static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
{
    struct map_info *map = mtd->priv;

    map_copy_from(map, buf, from, len);
    *retlen = len;
    return 0;
}

static int mapram_write (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
{
    struct map_info *map = mtd->priv;

    map_copy_to(map, to, buf, len);
    *retlen = len;
    return 0;
}

static int mapram_erase (struct mtd_info *mtd, struct erase_info *instr)
{
    /* Yeah, it's inefficient. Who cares? It's faster than a _real_
       flash erase. */
    struct map_info *map = mtd->priv;
    map_word allff;
    unsigned long i;

    allff = map_word_ff(map);
    for (i=0; i<instr->len; i += map_bankwidth(map))
        map_write(map, allff, instr->addr + i);
    instr->state = MTD_ERASE_DONE;
    mtd_erase_callback(instr);
    return 0;
}

static void mapram_nop(struct mtd_info *mtd)
{
    /* Nothing to see here */
}

static int __init map_ram_init(void)
{
    register_mtd_chip_driver(&mapram_chipdrv);
    return 0;
}

static void __exit map_ram_exit(void)
{
    unregister_mtd_chip_driver(&mapram_chipdrv);
}

module_init(map_ram_init);
module_exit(map_ram_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Woodhouse <[email protected]>");
MODULE_DESCRIPTION("MTD chip driver for RAM chips");