drivers/mfd/wm831x-otp.c

   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 */
  30 static 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
  46 static 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 rval;
  51         char id[WM831X_UNIQUE_ID_LEN];
  52
  53         rval = wm831x_unique_id_read(wm831x, id);
  54         if (rval < 0)
  55                 return 0;
  56
  57         return sprintf(buf, "%*phN\n", WM831X_UNIQUE_ID_LEN, id);
  58 }
  59
  60 static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
  61
  62 int wm831x_otp_init(struct wm831x *wm831x)
  63 {
  64         char uuid[WM831X_UNIQUE_ID_LEN];
  65         int ret;
  66
  67         ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
  68         if (ret != 0)
  69                 dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
  70                         ret);
  71
  72         ret = wm831x_unique_id_read(wm831x, uuid);
  73         if (ret == 0)
  74                 add_device_randomness(uuid, sizeof(uuid));
  75         else
  76                 dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
  77
  78         return ret;
  79 }
  80
  81 void wm831x_otp_exit(struct wm831x *wm831x)
  82 {
  83         device_remove_file(wm831x->dev, &dev_attr_unique_id);
  84 }
  85