LXR linux/drivers/mfd/wm831x-otp.c

   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, "%*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        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(wm831x->dev, &dev_attr_unique_id);
  79}
  80
  81