[PATCH] tpm: Add module parameter for hwrng quality.

Louis Collard
2018-06-08T06:54:48Z

It is now possible for drivers to easily specify a hwrng quality, however
most do not currently do this, and in cases where they do, it may be
desirable to override the driver-specified value with a user-specified
one. This patch adds a parameter to set or override the hwrng quality.

Signed-off-by: Louis Collard <louiscollard@chromium.org>
---
drivers/char/tpm/tpm-chip.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 0a62c19937b6..4def49cfc634 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -33,6 +33,11 @@
DEFINE_IDR(dev_nums_idr);
static DEFINE_MUTEX(idr_lock);

+static short override_rng_quality = -1;
+module_param(override_rng_quality, short, 0644);
+MODULE_PARM_DESC(override_rng_quality,
+ "tpm-rng quality (overrides values provided by drivers)");
+
struct class *tpm_class;
struct class *tpmrm_class;
dev_t tpm_devt;
@@ -409,6 +414,13 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
"tpm-rng-%d", chip->dev_num);
chip->hwrng.name = chip->hwrng_name;
chip->hwrng.read = tpm_hwrng_read;
+ if (override_rng_quality > -1) {
+ dev_info(&chip->dev,
+ "Overriding hwrng quality for %s: driver default=%d, override=%d",
+ chip->hwrng.name, chip->hwrng.quality,
+ override_rng_quality);
+ chip->hwrng.quality = override_rng_quality;
+ }
return hwrng_register(&chip->hwrng);
}

--
2.13.5