generic_nvram.c

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/*
 * Generic /dev/nvram driver for architectures providing some
 * "generic" hooks, that is :
 *
 * nvram_read_byte, nvram_write_byte, nvram_sync, nvram_get_size
 *
 * Note that an additional hook is supported for PowerMac only
 * for getting the nvram "partition" informations
 *
 */

#define NVRAM_VERSION "1.1"

#include <linux/module.h>

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <asm/nvram.h>
#ifdef CONFIG_PPC_PMAC
#include <asm/machdep.h>
#endif

#define NVRAM_SIZE  8192

static DEFINE_MUTEX(nvram_mutex);
static ssize_t nvram_len;

static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
{
    switch (origin) {
    case 0:
        break;
    case 1:
        offset += file->f_pos;
        break;
    case 2:
        offset += nvram_len;
        break;
    default:
        offset = -1;
    }
    if (offset < 0)
        return -EINVAL;

    file->f_pos = offset;

    return file->f_pos;
}

static ssize_t read_nvram(struct file *file, char __user *buf,
              size_t count, loff_t *ppos)
{
    unsigned int i;
    char __user *p = buf;

    if (!access_ok(VERIFY_WRITE, buf, count))
        return -EFAULT;
    if (*ppos >= nvram_len)
        return 0;
    for (i = *ppos; count > 0 && i < nvram_len; ++i, ++p, --count)
        if (__put_user(nvram_read_byte(i), p))
            return -EFAULT;
    *ppos = i;
    return p - buf;
}

static ssize_t write_nvram(struct file *file, const char __user *buf,
               size_t count, loff_t *ppos)
{
    unsigned int i;
    const char __user *p = buf;
    char c;

    if (!access_ok(VERIFY_READ, buf, count))
        return -EFAULT;
    if (*ppos >= nvram_len)
        return 0;
    for (i = *ppos; count > 0 && i < nvram_len; ++i, ++p, --count) {
        if (__get_user(c, p))
            return -EFAULT;
        nvram_write_byte(c, i);
    }
    *ppos = i;
    return p - buf;
}

static int nvram_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    switch(cmd) {
#ifdef CONFIG_PPC_PMAC
    case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
        printk(KERN_WARNING "nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n");
    case IOC_NVRAM_GET_OFFSET: {
        int part, offset;

        if (!machine_is(powermac))
            return -EINVAL;
        if (copy_from_user(&part, (void __user*)arg, sizeof(part)) != 0)
            return -EFAULT;
        if (part < pmac_nvram_OF || part > pmac_nvram_NR)
            return -EINVAL;
        offset = pmac_get_partition(part);
        if (copy_to_user((void __user*)arg, &offset, sizeof(offset)) != 0)
            return -EFAULT;
        break;
    }
#endif /* CONFIG_PPC_PMAC */
    case IOC_NVRAM_SYNC:
        nvram_sync();
        break;
    default:
        return -EINVAL;
    }

    return 0;
}

static long nvram_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    int ret;

    mutex_lock(&nvram_mutex);
    ret = nvram_ioctl(file, cmd, arg);
    mutex_unlock(&nvram_mutex);

    return ret;
}

const struct file_operations nvram_fops = {
    .owner      = THIS_MODULE,
    .llseek     = nvram_llseek,
    .read       = read_nvram,
    .write      = write_nvram,
    .unlocked_ioctl = nvram_unlocked_ioctl,
};

static struct miscdevice nvram_dev = {
    NVRAM_MINOR,
    "nvram",
    &nvram_fops
};

int __init nvram_init(void)
{
    int ret = 0;

    printk(KERN_INFO "Generic non-volatile memory driver v%s\n",
        NVRAM_VERSION);
    ret = misc_register(&nvram_dev);
    if (ret != 0)
        goto out;

    nvram_len = nvram_get_size();
    if (nvram_len < 0)
        nvram_len = NVRAM_SIZE;

out:
    return ret;
}

void __exit nvram_cleanup(void)
{
        misc_deregister( &nvram_dev );
}

module_init(nvram_init);
module_exit(nvram_cleanup);
MODULE_LICENSE("GPL");