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_read(struct hwrng *rng, void *data, size_t max, bool wait)
  29 {
  30         u64 buffer[PLPAR_HCALL_BUFSIZE];
  31         size_t size = max < 8 ? max : 8;
  32         int rc;
  33
  34         rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
  35         if (rc != H_SUCCESS) {
  36                 pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
  37                 return -EIO;
  38         }
  39         memcpy(data, buffer, size);
  40
  41         /* The hypervisor interface returns 64 bits */
  42         return size;
  43 }
  44
  45 /**
  46  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
  47  *
  48  * This is a required function for a driver to operate in a CMO environment
  49  * but this device does not make use of DMA allocations, return 0.
  50  *
  51  * Return value:
  52  *      Number of bytes of IO data the driver will need to perform well -> 0
  53  */
  54 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
  55 {
  56         return 0;
  57 };
  58
  59 static struct hwrng pseries_rng = {
  60         .name           = KBUILD_MODNAME,
  61         .read           = pseries_rng_read,
  62 };
  63
  64 static int pseries_rng_probe(struct vio_dev *dev,
  65                 const struct vio_device_id *id)
  66 {
  67         return hwrng_register(&pseries_rng);
  68 }
  69
  70 static int pseries_rng_remove(struct vio_dev *dev)
  71 {
  72         hwrng_unregister(&pseries_rng);
  73         return 0;
  74 }
  75
  76 static struct vio_device_id pseries_rng_driver_ids[] = {
  77         { "ibm,random-v1", "ibm,random"},
  78         { "", "" }
  79 };
  80 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
  81
  82 static struct vio_driver pseries_rng_driver = {
  83         .name = KBUILD_MODNAME,
  84         .probe = pseries_rng_probe,
  85         .remove = pseries_rng_remove,
  86         .get_desired_dma = pseries_rng_get_desired_dma,
  87         .id_table = pseries_rng_driver_ids
  88 };
  89
  90 static int __init rng_init(void)
  91 {
  92         pr_info("Registering IBM pSeries RNG driver\n");
  93         return vio_register_driver(&pseries_rng_driver);
  94 }
  95
  96 module_init(rng_init);
  97
  98 static void __exit rng_exit(void)
  99 {
 100         vio_unregister_driver(&pseries_rng_driver);
 101 }
 102 module_exit(rng_exit);
 103
 104 MODULE_LICENSE("GPL");
 105 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
 106 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");