On Fri, 18 Dec 2020 19:29:12 -0700 Simon Glass sjg@chromium.org wrote:
int i;srand(get_ticks() + rand());
int i, ret;struct udevice *devp;u8 randv = 0;+#if defined(CONFIG_DM_RNG)
This seems a little backwards to me. The caller should request a RNG device, getting either a hardware one or a software one, and then call the uclass method to get the uuid.
Strictly speaking, there's no such thing as a "software RNG". The term "DRBG" was coined for accurateness, "deterministic random bit generator". The oxymoron "deterministic random" pretty much nails it. Alternatively, it can be called "pseudo" RNG. rand() and srand() exactly implement such a mechanism already, with low coding overhead. U-Boot runs fine with them most of the time, but there are rare cases where real entropy would be needed. This is what these two patches are about. In case there's more, I already speculated about a centralised entity in my response to the v1 cover letter, but for now these two changes should do.
ret = uclass_get_device(UCLASS_RNG, 0, &devp);if (ret) {ret = dm_rng_read(devp, &randv, sizeof(randv));if (ret < 0)randv = 0;}if (randv)srand(randv);else+#endif
srand(get_ticks() + rand()); /* Set all fields randomly */ for (i = 0; i < 4; i++)
[ rand() usage following here ^ ]
The #ifdefs are already gone in v3.
Torsten