cmd/rng.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * The 'rng' command prints bytes from the hardware random number generator.
   4  *
   5  * Copyright (c) 2019, Heinrich Schuchardt <xypron.glpk@gmx.de>
   6  */
   7 #include <common.h>
   8 #include <command.h>
   9 #include <dm.h>
  10 #include <hexdump.h>
  11 #include <malloc.h>
  12 #include <rng.h>
  13
  14 static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
  15 {
  16         size_t n;
  17         u8 buf[64];
  18         int devnum;
  19         struct udevice *dev;
  20         int ret = CMD_RET_SUCCESS;
  21
  22         switch (argc) {
  23         case 1:
  24                 devnum = 0;
  25                 n = 0x40;
  26                 break;
  27         case 2:
  28                 devnum = hextoul(argv[1], NULL);
  29                 n = 0x40;
  30                 break;
  31         case 3:
  32                 devnum = hextoul(argv[1], NULL);
  33                 n = hextoul(argv[2], NULL);
  34                 break;
  35         default:
  36                 return CMD_RET_USAGE;
  37         }
  38
  39         if (uclass_get_device_by_seq(UCLASS_RNG, devnum, &dev) || !dev) {
  40                 printf("No RNG device\n");
  41                 return CMD_RET_FAILURE;
  42         }
  43
  44         if (!n)
  45                 return 0;
  46
  47         n = min(n, sizeof(buf));
  48
  49         if (dm_rng_read(dev, buf, n)) {
  50                 printf("Reading RNG failed\n");
  51                 ret = CMD_RET_FAILURE;
  52         } else {
  53                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, buf, n);
  54         }
  55
  56         return ret;
  57 }
  58
  59 #ifdef CONFIG_SYS_LONGHELP
  60 static char rng_help_text[] =
  61         "[dev [n]]\n"
  62         "  - print n random bytes(max 64) read from dev\n";
  63 #endif
  64
  65 U_BOOT_CMD(
  66         rng, 3, 0, do_rng,
  67         "print bytes from the hardware random number generator",
  68         rng_help_text
  69 );