wm831x-otp.c
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/*
* wm831x-otp.c -- OTP for Wolfson WM831x PMICs
*
* Copyright 2009 Wolfson Microelectronics PLC.
*
* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/mfd/core.h>
#include <linux/random.h>
#include <linux/mfd/wm831x/core.h>
#include <linux/mfd/wm831x/otp.h>
/* In bytes */
#define WM831X_UNIQUE_ID_LEN 16
/* Read the unique ID from the chip into id */
static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
{
int i, val;
for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
if (val < 0)
return val;
id[i * 2] = (val >> 8) & 0xff;
id[(i * 2) + 1] = val & 0xff;
}
return 0;
}
static ssize_t wm831x_unique_id_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct wm831x *wm831x = dev_get_drvdata(dev);
int i, rval;
char id[WM831X_UNIQUE_ID_LEN];
ssize_t ret = 0;
rval = wm831x_unique_id_read(wm831x, id);
if (rval < 0)
return 0;
for (i = 0; i < WM831X_UNIQUE_ID_LEN; i++)
ret += sprintf(&buf[ret], "%02x", buf[i]);
ret += sprintf(&buf[ret], "\n");
return ret;
}
static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
int wm831x_otp_init(struct wm831x *wm831x)
{
char uuid[WM831X_UNIQUE_ID_LEN];
int ret;
ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
if (ret != 0)
dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
ret);
ret = wm831x_unique_id_read(wm831x, uuid);
if (ret == 0)
add_device_randomness(uuid, sizeof(uuid));
else
dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
return ret;
}
void wm831x_otp_exit(struct wm831x *wm831x)
{
device_remove_file(wm831x->dev, &dev_attr_unique_id);
}