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 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
60static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
61
62int 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
81void wm831x_otp_exit(struct wm831x *wm831x)
82{
83 device_remove_file(wm831x->dev, &dev_attr_unique_id);
84}
85
86