drivers/misc/eeprom/sunxi_sid.c

   1 /*
   2  * Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
   3  * http://www.linux-sunxi.org
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * This driver exposes the Allwinner security ID, efuses exported in byte-
  16  * sized chunks.
  17  */
  18
  19 #include <linux/compiler.h>
  20 #include <linux/device.h>
  21 #include <linux/err.h>
  22 #include <linux/export.h>
  23 #include <linux/fs.h>
  24 #include <linux/init.h>
  25 #include <linux/io.h>
  26 #include <linux/kernel.h>
  27 #include <linux/kobject.h>
  28 #include <linux/module.h>
  29 #include <linux/of_device.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/random.h>
  32 #include <linux/slab.h>
  33 #include <linux/stat.h>
  34 #include <linux/sysfs.h>
  35 #include <linux/types.h>
  36
  37 #define DRV_NAME "sunxi-sid"
  38
  39 struct sunxi_sid_data {
  40         void __iomem *reg_base;
  41         unsigned int keysize;
  42 };
  43
  44 /* We read the entire key, due to a 32 bit read alignment requirement. Since we
  45  * want to return the requested byte, this results in somewhat slower code and
  46  * uses 4 times more reads as needed but keeps code simpler. Since the SID is
  47  * only very rarely probed, this is not really an issue.
  48  */
  49 static u8 sunxi_sid_read_byte(const struct sunxi_sid_data *sid_data,
  50                               const unsigned int offset)
  51 {
  52         u32 sid_key;
  53
  54         if (offset >= sid_data->keysize)
  55                 return 0;
  56
  57         sid_key = ioread32be(sid_data->reg_base + round_down(offset, 4));
  58         sid_key >>= (offset % 4) * 8;
  59
  60         return sid_key; /* Only return the last byte */
  61 }
  62
  63 static ssize_t sid_read(struct file *fd, struct kobject *kobj,
  64                         struct bin_attribute *attr, char *buf,
  65                         loff_t pos, size_t size)
  66 {
  67         struct platform_device *pdev;
  68         struct sunxi_sid_data *sid_data;
  69         int i;
  70
  71         pdev = to_platform_device(kobj_to_dev(kobj));
  72         sid_data = platform_get_drvdata(pdev);
  73
  74         if (pos < 0 || pos >= sid_data->keysize)
  75                 return 0;
  76         if (size > sid_data->keysize - pos)
  77                 size = sid_data->keysize - pos;
  78
  79         for (i = 0; i < size; i++)
  80                 buf[i] = sunxi_sid_read_byte(sid_data, pos + i);
  81
  82         return i;
  83 }
  84
  85 static struct bin_attribute sid_bin_attr = {
  86         .attr = { .name = "eeprom", .mode = S_IRUGO, },
  87         .read = sid_read,
  88 };
  89
  90 static int sunxi_sid_remove(struct platform_device *pdev)
  91 {
  92         device_remove_bin_file(&pdev->dev, &sid_bin_attr);
  93         dev_dbg(&pdev->dev, "driver unloaded\n");
  94
  95         return 0;
  96 }
  97
  98 static const struct of_device_id sunxi_sid_of_match[] = {
  99         { .compatible = "allwinner,sun4i-sid", .data = (void *)16},
 100         { .compatible = "allwinner,sun7i-a20-sid", .data = (void *)512},
 101         {/* sentinel */},
 102 };
 103 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 104
 105 static int sunxi_sid_probe(struct platform_device *pdev)
 106 {
 107         struct sunxi_sid_data *sid_data;
 108         struct resource *res;
 109         const struct of_device_id *of_dev_id;
 110         u8 *entropy;
 111         unsigned int i;
 112
 113         sid_data = devm_kzalloc(&pdev->dev, sizeof(struct sunxi_sid_data),
 114                                 GFP_KERNEL);
 115         if (!sid_data)
 116                 return -ENOMEM;
 117
 118         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 119         sid_data->reg_base = devm_ioremap_resource(&pdev->dev, res);
 120         if (IS_ERR(sid_data->reg_base))
 121                 return PTR_ERR(sid_data->reg_base);
 122
 123         of_dev_id = of_match_device(sunxi_sid_of_match, &pdev->dev);
 124         if (!of_dev_id)
 125                 return -ENODEV;
 126         sid_data->keysize = (int)of_dev_id->data;
 127
 128         platform_set_drvdata(pdev, sid_data);
 129
 130         sid_bin_attr.size = sid_data->keysize;
 131         if (device_create_bin_file(&pdev->dev, &sid_bin_attr))
 132                 return -ENODEV;
 133
 134         entropy = kzalloc(sizeof(u8) * sid_data->keysize, GFP_KERNEL);
 135         for (i = 0; i < sid_data->keysize; i++)
 136                 entropy[i] = sunxi_sid_read_byte(sid_data, i);
 137         add_device_randomness(entropy, sid_data->keysize);
 138         kfree(entropy);
 139
 140         dev_dbg(&pdev->dev, "loaded\n");
 141
 142         return 0;
 143 }
 144
 145 static struct platform_driver sunxi_sid_driver = {
 146         .probe = sunxi_sid_probe,
 147         .remove = sunxi_sid_remove,
 148         .driver = {
 149                 .name = DRV_NAME,
 150                 .owner = THIS_MODULE,
 151                 .of_match_table = sunxi_sid_of_match,
 152         },
 153 };
 154 module_platform_driver(sunxi_sid_driver);
 155
 156 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 157 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 158 MODULE_LICENSE("GPL");