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