81 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * wm831x-otp.c -- OTP for Wolfson WM831x PMICs4 *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 1623 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, "%*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(wm831x->dev, &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, uuid);68 if (ret == 0)69 add_device_randomness(uuid, sizeof(uuid));70 else71 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(wm831x->dev, &dev_attr_unique_id);79}80 81