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 */
  25 static 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
  41 static 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
  55 static DEVICE_ATTR_RO(unique_id);
  56
  57 int 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
  76 void wm831x_otp_exit(struct wm831x *wm831x)
  77 {
  78         device_remove_file(wm831x->dev, &dev_attr_unique_id);
  79 }
  80