drivers/mfd/wm831x-otp.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * wm831x-otp.c  --  OTP for Wolfson WM831x PMICs
0004  *
0005  * Copyright 2009 Wolfson Microelectronics PLC.
0006  *
0007  * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
0008  */
0009
0010 #include <linux/kernel.h>
0011 #include <linux/module.h>
0012 #include <linux/i2c.h>
0013 #include <linux/bcd.h>
0014 #include <linux/delay.h>
0015 #include <linux/mfd/core.h>
0016 #include <linux/random.h>
0017
0018 #include <linux/mfd/wm831x/core.h>
0019 #include <linux/mfd/wm831x/otp.h>
0020
0021 /* In bytes */
0022 #define WM831X_UNIQUE_ID_LEN 16
0023
0024 /* Read the unique ID from the chip into id */
0025 static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
0026 {
0027     int i, val;
0028
0029     for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
0030         val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
0031         if (val < 0)
0032             return val;
0033
0034         id[i * 2]       = (val >> 8) & 0xff;
0035         id[(i * 2) + 1] = val & 0xff;
0036     }
0037
0038     return 0;
0039 }
0040
0041 static ssize_t unique_id_show(struct device *dev,
0042                   struct device_attribute *attr, char *buf)
0043 {
0044     struct wm831x *wm831x = dev_get_drvdata(dev);
0045     int rval;
0046     char id[WM831X_UNIQUE_ID_LEN];
0047
0048     rval = wm831x_unique_id_read(wm831x, id);
0049     if (rval < 0)
0050         return 0;
0051
0052     return sprintf(buf, "%*phN\n", WM831X_UNIQUE_ID_LEN, id);
0053 }
0054
0055 static DEVICE_ATTR_RO(unique_id);
0056
0057 int wm831x_otp_init(struct wm831x *wm831x)
0058 {
0059     char uuid[WM831X_UNIQUE_ID_LEN];
0060     int ret;
0061
0062     ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
0063     if (ret != 0)
0064         dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
0065             ret);
0066
0067     ret = wm831x_unique_id_read(wm831x, uuid);
0068     if (ret == 0)
0069         add_device_randomness(uuid, sizeof(uuid));
0070     else
0071         dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
0072
0073     return ret;
0074 }
0075
0076 void wm831x_otp_exit(struct wm831x *wm831x)
0077 {
0078     device_remove_file(wm831x->dev, &dev_attr_unique_id);
0079 }
0080