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/*
* Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
* http://www.linux-sunxi.org
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* This driver exposes the Allwinner security ID, efuses exported in byte-
* sized chunks.
*/
#include <linux/compiler.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/sysfs.h>
#include <linux/types.h>
#define DRV_NAME "sunxi-sid"
struct sunxi_sid_data {
void __iomem *reg_base;
unsigned int keysize;
};
/* We read the entire key, due to a 32 bit read alignment requirement. Since we
* want to return the requested byte, this results in somewhat slower code and
* uses 4 times more reads as needed but keeps code simpler. Since the SID is
* only very rarely probed, this is not really an issue.
*/
static u8 sunxi_sid_read_byte(const struct sunxi_sid_data *sid_data,
const unsigned int offset)
{
u32 sid_key;
if (offset >= sid_data->keysize)
return 0;
sid_key = ioread32be(sid_data->reg_base + round_down(offset, 4));
sid_key >>= (offset % 4) * 8;
return sid_key; /* Only return the last byte */
}
static ssize_t sid_read(struct file *fd, struct kobject *kobj,
struct bin_attribute *attr, char *buf,
loff_t pos, size_t size)
{
struct platform_device *pdev;
struct sunxi_sid_data *sid_data;
int i;
pdev = to_platform_device(kobj_to_dev(kobj));
sid_data = platform_get_drvdata(pdev);
if (pos < 0 || pos >= sid_data->keysize)
return 0;
if (size > sid_data->keysize - pos)
size = sid_data->keysize - pos;
for (i = 0; i < size; i++)
buf[i] = sunxi_sid_read_byte(sid_data, pos + i);
return i;
}
static struct bin_attribute sid_bin_attr = {
.attr = { .name = "eeprom", .mode = S_IRUGO, },
.read = sid_read,
};
static int sunxi_sid_remove(struct platform_device *pdev)
{
device_remove_bin_file(&pdev->dev, &sid_bin_attr);
dev_dbg(&pdev->dev, "driver unloaded\n");
return 0;
}
static const struct of_device_id sunxi_sid_of_match[] = {
{ .compatible = "allwinner,sun4i-sid", .data = (void *)16},
{ .compatible = "allwinner,sun7i-a20-sid", .data = (void *)512},
{/* sentinel */},
};
MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
static int sunxi_sid_probe(struct platform_device *pdev)
{
struct sunxi_sid_data *sid_data;
struct resource *res;
const struct of_device_id *of_dev_id;
u8 *entropy;
unsigned int i;
sid_data = devm_kzalloc(&pdev->dev, sizeof(struct sunxi_sid_data),
GFP_KERNEL);
if (!sid_data)
return -ENOMEM;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
sid_data->reg_base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(sid_data->reg_base))
return PTR_ERR(sid_data->reg_base);
of_dev_id = of_match_device(sunxi_sid_of_match, &pdev->dev);
if (!of_dev_id)
return -ENODEV;
sid_data->keysize = (int)of_dev_id->data;
platform_set_drvdata(pdev, sid_data);
sid_bin_attr.size = sid_data->keysize;
if (device_create_bin_file(&pdev->dev, &sid_bin_attr))
return -ENODEV;
entropy = kzalloc(sizeof(u8) * sid_data->keysize, GFP_KERNEL);
for (i = 0; i < sid_data->keysize; i++)
entropy[i] = sunxi_sid_read_byte(sid_data, i);
add_device_randomness(entropy, sid_data->keysize);
kfree(entropy);
dev_dbg(&pdev->dev, "loaded\n");
return 0;
}
static struct platform_driver sunxi_sid_driver = {
.probe = sunxi_sid_probe,
.remove = sunxi_sid_remove,
.driver = {
.name = DRV_NAME,
.owner = THIS_MODULE,
.of_match_table = sunxi_sid_of_match,
},
};
module_platform_driver(sunxi_sid_driver);
MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
MODULE_DESCRIPTION("Allwinner sunxi security id driver");
MODULE_LICENSE("GPL");
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