[PATCH v2 3/5] doc: document read/write commands

[Rasmus Villemoes]

Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
---
 doc/usage/cmd/read.rst | 40 ++++++++++++++++++++++++++++++++++++++++
 doc/usage/index.rst    |  1 +
 2 files changed, 41 insertions(+)
 create mode 100644 doc/usage/cmd/read.rst

diff --git a/doc/usage/cmd/read.rst b/doc/usage/cmd/read.rst
new file mode 100644
index 0000000000..705d5a3e0c
--- /dev/null
+++ b/doc/usage/cmd/read.rst
@@ -0,0 +1,40 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+read/write commands
+===================
+
+Synopsis
+--------
+
+::
+
+    read <interface> <dev[:part|#partname]> <addr> <blk#> <cnt>
+    write <interface> <dev[:part|#partname]> <addr> <blk#> <cnt>
+
+The read and write commands can be used for raw access to data in
+block devices (or partitions therein), i.e. without going through a
+file system.
+
+read
+----
+
+The block device is specified using the <interface> (e.g. "mmc") and
+<dev> parameters. If the block device has a partition table, one can
+optionally specify a partition number (using the :part syntax) or
+partition name (using the #partname syntax). The command then reads
+the <cnt> blocks of data starting at block number <blk#> of the given
+device/partition to the memory address <addr>.
+
+Examples:
+
+    # Read 2 MiB from partition 3 of mmc device 2 to $loadaddr
+    read mmc 2.3 $loadaddr 0 0x1000
+
+    # Read 16 MiB from the partition named 'kernel' of mmc device 1 to $loadaddr
+    read mmc 1#kernel $loadaddr 0 0x8000
+
+write
+-----
+
+The write command is completely equivalent to the read command, except
+of course that the transer direction is reversed.
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index 840c20c934..d6365cf8a4 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -71,6 +71,7 @@ Shell commands
    cmd/printenv
    cmd/pstore
    cmd/qfw
+   cmd/read
    cmd/reset
    cmd/rng
    cmd/sbi
-- 
2.37.2