phram.c

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#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 <[email protected]>");
MODULE_DESCRIPTION("MTD driver for physical RAM");