1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * wm831x-otp.c -- OTP for Wolfson WM831x PMICs
4 *
5 * Copyright 2009 Wolfson Microelectronics PLC.
6 *
7 * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
8 */
9
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/i2c.h>
13#include <linux/bcd.h>
14#include <linux/delay.h>
15#include <linux/mfd/core.h>
16#include <linux/random.h>
17
18#include <linux/mfd/wm831x/core.h>
19#include <linux/mfd/wm831x/otp.h>
20
21/* In bytes */
22#define WM831X_UNIQUE_ID_LEN 16
23
24/* Read the unique ID from the chip into id */
25static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
26{
27 int i, val;
28
29 for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
30 val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
31 if (val < 0)
32 return val;
33
34 id[i * 2] = (val >> 8) & 0xff;
35 id[(i * 2) + 1] = val & 0xff;
36 }
37
38 return 0;
39}
40
41static ssize_t unique_id_show(struct device *dev,
42 struct device_attribute *attr, char *buf)
43{
44 struct wm831x *wm831x = dev_get_drvdata(dev);
45 int rval;
46 char id[WM831X_UNIQUE_ID_LEN];
47
48 rval = wm831x_unique_id_read(wm831x, id);
49 if (rval < 0)
50 return 0;
51
52 return sprintf(buf, fmt: "%*phN\n", WM831X_UNIQUE_ID_LEN, id);
53}
54
55static DEVICE_ATTR_RO(unique_id);
56
57int wm831x_otp_init(struct wm831x *wm831x)
58{
59 char uuid[WM831X_UNIQUE_ID_LEN];
60 int ret;
61
62 ret = device_create_file(device: wm831x->dev, entry: &dev_attr_unique_id);
63 if (ret != 0)
64 dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
65 ret);
66
67 ret = wm831x_unique_id_read(wm831x, id: uuid);
68 if (ret == 0)
69 add_device_randomness(buf: uuid, len: sizeof(uuid));
70 else
71 dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
72
73 return ret;
74}
75
76void wm831x_otp_exit(struct wm831x *wm831x)
77{
78 device_remove_file(dev: wm831x->dev, attr: &dev_attr_unique_id);
79}
80
81

source code of linux/drivers/mfd/wm831x-otp.c