[PATCH 4.9 081/264] random: document add_hwgenerator_randomness() with other input functions

Greg Kroah-Hartman
2022-06-23T16:58:42Z

From: Mark Brown <broonie@kernel.org>

commit 2b6c6e3d9ce3aa0e547ac25d60e06fe035cd9f79 upstream.

The section at the top of random.c which documents the input functions
available does not document add_hwgenerator_randomness() which might lead
a reader to overlook it. Add a brief note about it.

Signed-off-by: Mark Brown <broonie@kernel.org>
[Jason: reorganize position of function in doc comment and also document
add_bootloader_randomness() while we're at it.]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/random.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -202,6 +202,9 @@
* unsigned int value);
* void add_interrupt_randomness(int irq, int irq_flags);
* void add_disk_randomness(struct gendisk *disk);
+ * void add_hwgenerator_randomness(const char *buffer, size_t count,
+ * size_t entropy);
+ * void add_bootloader_randomness(const void *buf, unsigned int size);
*
* add_device_randomness() is for adding data to the random pool that
* is likely to differ between two devices (or possibly even per boot).
@@ -228,6 +231,14 @@
* particular randomness source. They do this by keeping track of the
* first and second order deltas of the event timings.
*
+ * add_hwgenerator_randomness() is for true hardware RNGs, and will credit
+ * entropy as specified by the caller. If the entropy pool is full it will
+ * block until more entropy is needed.
+ *
+ * add_bootloader_randomness() is the same as add_hwgenerator_randomness() or
+ * add_device_randomness(), depending on whether or not the configuration
+ * option CONFIG_RANDOM_TRUST_BOOTLOADER is set.
+ *
* Ensuring unpredictability at system startup
* ============================================
*