doc: rng: Add documentation for the rng command

Add a usage document for the 'rng' u-boot command.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/doc/usage/cmd/rng.rst b/doc/usage/cmd/rng.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+rng command
+===========
+
+Synopsis
+--------
+
+::
+
+    rng [devnum [n]]
+
+Description
+-----------
+
+The *rng* command reads the random number generator(RNG) device and
+prints the random bytes read on the console. A maximum of 64 bytes can
+be read in one invocation of the command.
+
+devnum
+    The RNG device from which the random bytes are to be
+    read. Defaults to 0.
+
+n
+    Number of random bytes to be read and displayed on the
+    console. Default value is 0x40. Max value is 0x40.