linux-kernel - [PATCH 4.19 048/234] random: document add_hwgenerator

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Message-Id: <20220623164344.426289839@linuxfoundation.org>
Date:   Thu, 23 Jun 2022 18:41:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 4.19 048/234] random: document add_hwgenerator_randomness() with other input functions

From: Mark Brown <broonie@...nel.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@...nel.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@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
  * ============================================
  *