at86rf2xx_internal: Don't get a random number with the function at86rf2xx_get_random

[RocioRojas]

Description

I need to get a seed cryptographically secure and I used the PR #4989, but the test described in that PR won't work with the board samr21-xpro.

Steps to reproduce the issue

Tested with the following change in file tests/driver_at86rf2xx/main.c on samr21-xpro board :

   for (int i = 0; i < 10; i++) {
       unsigned int test = 0;
        at86rf2xx_get_random(devs, (uint8_t *)&test, sizeof(test));
        printf("%08x\n", test);
  }

Expected results

If I put this line:

prev_state = at86rf2xx_set_state(dev, AT86RF2XX_STATE_SLEEP);

at the end of at86rf2xx_configure_phy function in drivers/at86rf2xx/at86rf2xx_internal.c

The results are:

2022-06-28 23:39:54,159 # Initialization successful - starting the shell now
> 2022-06-28 23:39:56,422 # main(): This is RIOT! (Version: 2021.10-devel-4249-g5f574-HEAD)
2022-06-28 23:39:56,424 # AT86RF2xx device driver test
2022-06-28 23:39:56,428 # Initializing AT86RF2xx radio at SPI_0
2022-06-28 23:39:56,432 # a4cebbd9
2022-06-28 23:39:56,434 # e28fc5e1
2022-06-28 23:39:56,435 # 02161afd
2022-06-28 23:39:56,436 # 71cd3348
2022-06-28 23:39:56,437 # 772d4273
2022-06-28 23:39:56,438 # 07c145b7
2022-06-28 23:39:56,440 # 1340606d
2022-06-28 23:39:56,441 # 99afd90d
2022-06-28 23:39:56,442 # 593021bc
2022-06-28 23:39:56,443 # f790bba0
2022-06-28 23:39:56,448 # Initialization successful - starting the shell now

Note: when I reset the device I get different randoms numbers.

The problem with this solution is that I don't know how this change affects other parts on the module.

Actual results

I get the following answer:

2022-06-28 23:39:26,082 # AT86RF2xx device driver test
2022-06-28 23:39:26,086 # Initializing AT86RF2xx radio at SPI_0
2022-06-28 23:39:26,092 # gnrc_netdev: possibly lost interrupt.
2022-06-28 23:39:26,093 # ffffffff
2022-06-28 23:39:26,094 # ffffffff
2022-06-28 23:39:26,096 # ffffffff
2022-06-28 23:39:26,097 # ffffffff
2022-06-28 23:39:26,098 # ffffffff
2022-06-28 23:39:26,099 # ffffffff
2022-06-28 23:39:26,101 # ffffffff
2022-06-28 23:39:26,102 # ffffffff
2022-06-28 23:39:26,103 # ffffffff
2022-06-28 23:39:26,104 # ffffffff
2022-06-28 23:39:26,109 # Initialization successful - starting the shell now
> 2022-06-28 23:39:38,542 # Exiting Pyterm

Versions

RIOT version Release 2022.04