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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 */ |
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 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 | |
66 | static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL); |
67 | |
68 | int 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 | |
87 | void wm831x_otp_exit(struct wm831x *wm831x) |
88 | { |
89 | device_remove_file(wm831x->dev, &dev_attr_unique_id); |
90 | } |
91 | |
92 |
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