Merge branch '2021-08-02-numeric-input-cleanups'

- Merge in a series that cleans up and makes more consistent how we deal
  with numeric input on the CLI.  This saves a few bytes in a lot of
  places.

2 files changed, 94 insertions, 0 deletions

diff --git a/doc/usage/cmdline.rst b/doc/usage/cmdline.rst
new file mode 100644
index 00000000000..88f18c974c8
--- /dev/null
+++ b/doc/usage/cmdline.rst
@@ -0,0 +1,93 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Command-line Parsing
+====================
+
+The command line is available in U-Boot proper, enabled by CONFIG_CMDLINE which
+is on by default. It is not enabled in SPL.
+
+There are two different command-line parsers available with U-Boot:
+the old "simple" one, and the much more powerful "hush" shell:
+
+Simple command-line parser
+--------------------------
+
+This takes very little code space and offers only basic features:
+
+- supports environment variables (through setenv / saveenv commands)
+- several commands on one line, separated by ';'
+- variable substitution using "... ${name} ..." syntax
+- special characters ('$', ';') can be escaped by prefixing with '\',
+  for example::
+
+    setenv bootcmd bootm \${address}
+
+- You can also escape text by enclosing in single apostrophes, for example::
+
+    setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
+
+Hush shell
+----------
+
+This is similar to Bourne shell, with control structures like:
+
+- `if`... `then` ... `else`... `fi`
+- `for`... `do` ... `done`
+- `while` ... `do` ... `done`
+- `until` ... `do` ... `done`
+
+Hush supports environment ("global") variables (through setenv / saveenv
+commands) and local shell variables (through standard shell syntax
+`name=value`); only environment variables can be used with the "run" command
+
+The Hush shell is enabled with `CONFIG_HUSH_PARSER`.
+
+General rules
+-------------
+
+#. If a command line (or an environment variable executed by a "run"
+   command) contains several commands separated by semicolon, and
+   one of these commands fails, then the remaining commands will be
+   executed anyway.
+
+#. If you execute several variables with one call to run (i. e.
+   calling run with a list of variables as arguments), any failing
+   command will cause "run" to terminate, i. e. the remaining
+   variables are not executed.
+
+Representing numbers
+--------------------
+
+Most U-Boot commands use hexadecimal (hex) as the default base, for convenient
+use of addresses, for example::
+
+  => md 1000 6
+  00001000: 2c786f62 00697073 03000000 0c000000  box,spi.........
+  00001010: 67020000 00000000                    ...g....
+
+There is no need to add a `0x` prefix to the arguments and the output is shown
+in hex also, without any prefixes. This helps to avoid clutter.
+
+Some commands use decimal where it is more natural::
+
+  => i2c dev 0
+  Setting bus to 0
+  => i2c speed
+  Current bus speed=400000
+  => i2c speed 100000
+  Setting bus speed to 100000 Hz
+
+In some cases the default is decimal but it is possible to use octal if that is
+useful::
+
+  pmic dev pmic@41
+  dev: 1 @ pmic@41
+  => pmic write 2 0177
+  => pmic read 2
+  0x02: 0x00007f
+
+It is possible to use a `0x` prefix to use a hex value if that is more
+convenient::
+
+  => i2c speed 0x30000
+  Setting bus speed to 196608 Hz
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index 719b2c90b9d..356f2a56181 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -9,6 +9,7 @@ Use U-Boot
    fit
    netconsole
    partitions
+   cmdline
 
 Shell commands
 --------------