/**
 * Copyright (c) ????           Jochen Schäuble <psionic@psionic.de>
 * Copyright (c) 2003-2004      Joern Engel <joern@wh.fh-wedel.de>
 *
 * Usage:
 *
 * one commend line parameter per device, each in the form:
 *   phram=<name>,<start>,<len>
 * <name> may be up to 63 characters.
 * <start> and <len> can be octal, decimal or hexadecimal.  If followed
 * by "ki", "Mi" or "Gi", the numbers will be interpreted as kilo, mega or
 * gigabytes.
 *
 * Example:
 *      phram=swap,64Mi,128Mi phram=test,900Mi,1Mi
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <asm/io.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>

struct phram_mtd_list {
        struct mtd_info mtd;
        struct list_head list;
};

static LIST_HEAD(phram_list);

static int phram_erase(struct mtd_info *mtd, struct erase_info *instr)
{
        u_char *start = mtd->priv;

        memset(start + instr->addr, 0xff, instr->len);

        /*
         * This'll catch a few races. Free the thing before returning :)
         * I don't feel at all ashamed. This kind of thing is possible anyway
         * with flash, but unlikely.
         */
        instr->state = MTD_ERASE_DONE;
        mtd_erase_callback(instr);
        return 0;
}

static int phram_point(struct mtd_info *mtd, loff_t from, size_t len,
                size_t *retlen, void **virt, resource_size_t *phys)
{
        *virt = mtd->priv + from;
        *retlen = len;
        return 0;
}

static int phram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
{
        return 0;
}

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

        memcpy(buf, start + from, len);
        *retlen = len;
        return 0;
}

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

        memcpy(start + to, buf, len);
        *retlen = len;
        return 0;
}

static void unregister_devices(void)
{
        struct phram_mtd_list *this, *safe;

        list_for_each_entry_safe(this, safe, &phram_list, list) {
                mtd_device_unregister(&this->mtd);
                iounmap(this->mtd.priv);
                kfree(this->mtd.name);
                kfree(this);
        }
}

static int register_device(char *name, unsigned long start, unsigned long len)
{
        struct phram_mtd_list *new;
        int ret = -ENOMEM;

        new = kzalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out0;

        ret = -EIO;
        new->mtd.priv = ioremap(start, len);
        if (!new->mtd.priv) {
                pr_err("ioremap failed\n");
                goto out1;
        }


        new->mtd.name = name;
        new->mtd.size = len;
        new->mtd.flags = MTD_CAP_RAM;
        new->mtd._erase = phram_erase;
        new->mtd._point = phram_point;
        new->mtd._unpoint = phram_unpoint;
        new->mtd._read = phram_read;
        new->mtd._write = phram_write;
        new->mtd.owner = THIS_MODULE;
        new->mtd.type = MTD_RAM;
        new->mtd.erasesize = PAGE_SIZE;
        new->mtd.writesize = 1;

        ret = -EAGAIN;
        if (mtd_device_register(&new->mtd, NULL, 0)) {
                pr_err("Failed to register new device\n");
                goto out2;
        }

        list_add_tail(&new->list, &phram_list);
        return 0;

out2:
        iounmap(new->mtd.priv);
out1:
        kfree(new);
out0:
        return ret;
}

static int ustrtoul(const char *cp, char **endp, unsigned int base)
{
        unsigned long result = simple_strtoul(cp, endp, base);

        switch (**endp) {
        case 'G':
                result *= 1024;
        case 'M':
                result *= 1024;
        case 'k':
                result *= 1024;
        /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
                if ((*endp)[1] == 'i')
                        (*endp) += 2;
        }
        return result;
}

static int parse_num32(uint32_t *num32, const char *token)
{
        char *endp;
        unsigned long n;

        n = ustrtoul(token, &endp, 0);
        if (*endp)
                return -EINVAL;

        *num32 = n;
        return 0;
}

static int parse_name(char **pname, const char *token)
{
        size_t len;
        char *name;

        len = strlen(token) + 1;
        if (len > 64)
                return -ENOSPC;

        name = kmalloc(len, GFP_KERNEL);
        if (!name)
                return -ENOMEM;

        strcpy(name, token);

        *pname = name;
        return 0;
}


static inline void kill_final_newline(char *str)
{
        char *newline = strrchr(str, '\n');
        if (newline && !newline[1])
                *newline = 0;
}


#define parse_err(fmt, args...) do {    \
        pr_err(fmt , ## args);  \
        return 1;               \
} while (0)

/*
 * This shall contain the module parameter if any. It is of the form:
 * - phram=<device>,<address>,<size> for module case
 * - phram.phram=<device>,<address>,<size> for built-in case
 * We leave 64 bytes for the device name, 12 for the address and 12 for the
 * size.
 * Example: phram.phram=rootfs,0xa0000000,512Mi
 */
static __initdata char phram_paramline[64+12+12];

static int __init phram_setup(const char *val)
{
        char buf[64+12+12], *str = buf;
        char *token[3];
        char *name;
        uint32_t start;
        uint32_t len;
        int i, ret;

        if (strnlen(val, sizeof(buf)) >= sizeof(buf))
                parse_err("parameter too long\n");

        strcpy(str, val);
        kill_final_newline(str);

        for (i=0; i<3; i++)
                token[i] = strsep(&str, ",");

        if (str)
                parse_err("too many arguments\n");

        if (!token[2])
                parse_err("not enough arguments\n");

        ret = parse_name(&name, token[0]);
        if (ret)
                return ret;

        ret = parse_num32(&start, token[1]);
        if (ret) {
                kfree(name);
                parse_err("illegal start address\n");
        }

        ret = parse_num32(&len, token[2]);
        if (ret) {
                kfree(name);
                parse_err("illegal device length\n");
        }

        ret = register_device(name, start, len);
        if (!ret)
                pr_info("%s device: %#x at %#x\n", name, len, start);
        else
                kfree(name);

        return ret;
}

static int __init phram_param_call(const char *val, struct kernel_param *kp)
{
        /*
         * This function is always called before 'init_phram()', whether
         * built-in or module.
         */
        if (strlen(val) >= sizeof(phram_paramline))
                return -ENOSPC;
        strcpy(phram_paramline, val);

        return 0;
}

module_param_call(phram, phram_param_call, NULL, NULL, 000);
MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>\"");


static int __init init_phram(void)
{
        if (phram_paramline[0])
                return phram_setup(phram_paramline);

        return 0;
}

static void __exit cleanup_phram(void)
{
        unregister_devices();
}

module_init(init_phram);
module_exit(cleanup_phram);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joern Engel <joern@wh.fh-wedel.de>");
MODULE_DESCRIPTION("MTD driver for physical RAM");