linux/drivers/mfd/wm831x-otp.c
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   1/*
   2 * wm831x-otp.c  --  OTP for Wolfson WM831x PMICs
   3 *
   4 * Copyright 2009 Wolfson Microelectronics PLC.
   5 *
   6 * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
   7 *
   8 *  This program is free software; you can redistribute  it and/or modify it
   9 *  under  the terms of  the GNU General  Public License as published by the
  10 *  Free Software Foundation;  either version 2 of the  License, or (at your
  11 *  option) any later version.
  12 *
  13 */
  14
  15#include <linux/kernel.h>
  16#include <linux/module.h>
  17#include <linux/i2c.h>
  18#include <linux/bcd.h>
  19#include <linux/delay.h>
  20#include <linux/mfd/core.h>
  21#include <linux/random.h>
  22
  23#include <linux/mfd/wm831x/core.h>
  24#include <linux/mfd/wm831x/otp.h>
  25
  26/* In bytes */
  27#define WM831X_UNIQUE_ID_LEN 16
  28
  29/* Read the unique ID from the chip into id */
  30static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
  31{
  32        int i, val;
  33
  34        for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
  35                val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
  36                if (val < 0)
  37                        return val;
  38
  39                id[i * 2]       = (val >> 8) & 0xff;
  40                id[(i * 2) + 1] = val & 0xff;
  41        }
  42
  43        return 0;
  44}
  45
  46static ssize_t wm831x_unique_id_show(struct device *dev,
  47                                     struct device_attribute *attr, char *buf)
  48{
  49        struct wm831x *wm831x = dev_get_drvdata(dev);
  50        int i, rval;
  51        char id[WM831X_UNIQUE_ID_LEN];
  52        ssize_t ret = 0;
  53
  54        rval = wm831x_unique_id_read(wm831x, id);
  55        if (rval < 0)
  56                return 0;
  57
  58        for (i = 0; i < WM831X_UNIQUE_ID_LEN; i++)
  59                ret += sprintf(&buf[ret], "%02x", buf[i]);
  60
  61        ret += sprintf(&buf[ret], "\n");
  62
  63        return ret;
  64}
  65
  66static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
  67
  68int wm831x_otp_init(struct wm831x *wm831x)
  69{
  70        char uuid[WM831X_UNIQUE_ID_LEN];
  71        int ret;
  72
  73        ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
  74        if (ret != 0)
  75                dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
  76                        ret);
  77
  78        ret = wm831x_unique_id_read(wm831x, uuid);
  79        if (ret == 0)
  80                add_device_randomness(uuid, sizeof(uuid));
  81        else
  82                dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
  83
  84        return ret;
  85}
  86
  87void wm831x_otp_exit(struct wm831x *wm831x)
  88{
  89        device_remove_file(wm831x->dev, &dev_attr_unique_id);
  90}
  91
  92
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