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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/hw_random.h>
  25 #include <asm/vio.h>
  26
  27
  28 static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
  29 {
  30         int rc;
  31
  32         rc = plpar_hcall(H_RANDOM, (unsigned long *)data);
  33         if (rc != H_SUCCESS) {
  34                 pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
  35                 return -EIO;
  36         }
  37
  38         /* The hypervisor interface returns 64 bits */
  39         return 8;
  40 }
  41
  42 /**
  43  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
  44  *
  45  * This is a required function for a driver to operate in a CMO environment
  46  * but this device does not make use of DMA allocations, return 0.
  47  *
  48  * Return value:
  49  *      Number of bytes of IO data the driver will need to perform well -> 0
  50  */
  51 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
  52 {
  53         return 0;
  54 };
  55
  56 static struct hwrng pseries_rng = {
  57         .name           = KBUILD_MODNAME,
  58         .data_read      = pseries_rng_data_read,
  59 };
  60
  61 static int __init pseries_rng_probe(struct vio_dev *dev,
  62                 const struct vio_device_id *id)
  63 {
  64         return hwrng_register(&pseries_rng);
  65 }
  66
  67 static int __exit pseries_rng_remove(struct vio_dev *dev)
  68 {
  69         hwrng_unregister(&pseries_rng);
  70         return 0;
  71 }
  72
  73 static struct vio_device_id pseries_rng_driver_ids[] = {
  74         { "ibm,random-v1", "ibm,random"},
  75         { "", "" }
  76 };
  77 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
  78
  79 static struct vio_driver pseries_rng_driver = {
  80         .name = KBUILD_MODNAME,
  81         .probe = pseries_rng_probe,
  82         .remove = pseries_rng_remove,
  83         .get_desired_dma = pseries_rng_get_desired_dma,
  84         .id_table = pseries_rng_driver_ids
  85 };
  86
  87 static int __init rng_init(void)
  88 {
  89         printk(KERN_INFO "Registering IBM pSeries RNG driver\n");
  90         return vio_register_driver(&pseries_rng_driver);
  91 }
  92
  93 module_init(rng_init);
  94
  95 static void __exit rng_exit(void)
  96 {
  97         vio_unregister_driver(&pseries_rng_driver);
  98 }
  99 module_exit(rng_exit);
 100
 101 MODULE_LICENSE("GPL");
 102 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
 103 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");