drivers/char/hw_random/pseries-rng.c

   1 /*
   2  * Copyright (C) 2010 Michael Neuling IBM Corporation
   3  *
   4  * Driver for the pseries hardware RNG for POWER7+ and above
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   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  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/hw_random.h>
  22 #include <asm/vio.h>
  23
  24 #define MODULE_NAME "pseries-rng"
  25
  26 static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
  27 {
  28         if (plpar_hcall(H_RANDOM, (unsigned long *)data) != H_SUCCESS) {
  29                 printk(KERN_ERR "pseries rng hcall error\n");
  30                 return 0;
  31         }
  32         return 8;
  33 }
  34
  35 /**
  36  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
  37  *
  38  * This is a required function for a driver to operate in a CMO environment
  39  * but this device does not make use of DMA allocations, return 0.
  40  *
  41  * Return value:
  42  *      Number of bytes of IO data the driver will need to perform well -> 0
  43  */
  44 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
  45 {
  46         return 0;
  47 };
  48
  49 static struct hwrng pseries_rng = {
  50         .name           = MODULE_NAME,
  51         .data_read      = pseries_rng_data_read,
  52 };
  53
  54 static int __init pseries_rng_probe(struct vio_dev *dev,
  55                 const struct vio_device_id *id)
  56 {
  57         return hwrng_register(&pseries_rng);
  58 }
  59
  60 static int __exit pseries_rng_remove(struct vio_dev *dev)
  61 {
  62         hwrng_unregister(&pseries_rng);
  63         return 0;
  64 }
  65
  66 static struct vio_device_id pseries_rng_driver_ids[] = {
  67         { "ibm,random-v1", "ibm,random"},
  68         { "", "" }
  69 };
  70 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
  71
  72 static struct vio_driver pseries_rng_driver = {
  73         .name = MODULE_NAME,
  74         .probe = pseries_rng_probe,
  75         .remove = pseries_rng_remove,
  76         .get_desired_dma = pseries_rng_get_desired_dma,
  77         .id_table = pseries_rng_driver_ids
  78 };
  79
  80 static int __init rng_init(void)
  81 {
  82         printk(KERN_INFO "Registering IBM pSeries RNG driver\n");
  83         return vio_register_driver(&pseries_rng_driver);
  84 }
  85
  86 module_init(rng_init);
  87
  88 static void __exit rng_exit(void)
  89 {
  90         vio_unregister_driver(&pseries_rng_driver);
  91 }
  92 module_exit(rng_exit);
  93
  94 MODULE_LICENSE("GPL");
  95 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
  96 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");