wm831x-otp.c

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/*
 * wm831x-otp.c  --  OTP for Wolfson WM831x PMICs
 *
 * Copyright 2009 Wolfson Microelectronics PLC.
 *
 * Author: Mark Brown <[email protected]>
 *
 *  This program is free software; you can redistribute  it and/or modify it
 *  under  the terms of  the GNU General  Public License as published by the
 *  Free Software Foundation;  either version 2 of the  License, or (at your
 *  option) any later version.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/mfd/core.h>
#include <linux/random.h>

#include <linux/mfd/wm831x/core.h>
#include <linux/mfd/wm831x/otp.h>

/* In bytes */
#define WM831X_UNIQUE_ID_LEN 16

/* Read the unique ID from the chip into id */
static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
{
    int i, val;

    for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
        val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
        if (val < 0)
            return val;

        id[i * 2]       = (val >> 8) & 0xff;
        id[(i * 2) + 1] = val & 0xff;
    }

    return 0;
}

static ssize_t wm831x_unique_id_show(struct device *dev,
                     struct device_attribute *attr, char *buf)
{
    struct wm831x *wm831x = dev_get_drvdata(dev);
    int i, rval;
    char id[WM831X_UNIQUE_ID_LEN];
    ssize_t ret = 0;

    rval = wm831x_unique_id_read(wm831x, id);
    if (rval < 0)
        return 0;

    for (i = 0; i < WM831X_UNIQUE_ID_LEN; i++)
        ret += sprintf(&buf[ret], "%02x", buf[i]);

    ret += sprintf(&buf[ret], "\n");

    return ret;
}

static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);

int wm831x_otp_init(struct wm831x *wm831x)
{
    char uuid[WM831X_UNIQUE_ID_LEN];
    int ret;

    ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
    if (ret != 0)
        dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
            ret);

    ret = wm831x_unique_id_read(wm831x, uuid);
    if (ret == 0)
        add_device_randomness(uuid, sizeof(uuid));
    else
        dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);

    return ret;
}

void wm831x_otp_exit(struct wm831x *wm831x)
{
    device_remove_file(wm831x->dev, &dev_attr_unique_id);
}