From 9769635423af703b131d7635e0de83767fe0006d Mon Sep 17 00:00:00 2001 From: Marco Felsch Date: Mon, 31 Aug 2020 16:00:42 +0200 Subject: [PATCH] hwrng: imx-rngc - add quality to use it as kernel entropy pool The RNGB can generate 2^20 words (1 word == 4 byte) of 'random' data after the seed pool was initialized. The pool needs to be reseeded if more words are required. The reseeding is done automatically since commit 3acd9ea9331c ("hwrng: imx-rngc - use automatic seeding"). We can't retrieve the TRNG values directly so we need a other way to get the quality level. We know that the PRNG uses 20.000 entropy samples from the TRNG to generate 2^20 words (1MiB) and the quality level is defined as (in bits of entropy per 1024 bits of input). So the quality level can be calculated by: 20.000 * 1024 ------------- = ~ 19.5 2^20 Signed-off-by: Marco Felsch Signed-off-by: Herbert Xu --- drivers/char/hw_random/imx-rngc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c index 9c47e43..61c844b 100644 --- a/drivers/char/hw_random/imx-rngc.c +++ b/drivers/char/hw_random/imx-rngc.c @@ -285,6 +285,7 @@ static int imx_rngc_probe(struct platform_device *pdev) rngc->rng.init = imx_rngc_init; rngc->rng.read = imx_rngc_read; rngc->rng.cleanup = imx_rngc_cleanup; + rngc->rng.quality = 19; rngc->dev = &pdev->dev; platform_set_drvdata(pdev, rngc); -- 2.7.4