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https://github.com/AsahiLinux/u-boot
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e6951139c0
U-Boot mostly uses hex for value input, largely because addresses are much easier to understand in hex. But in some cases a decimal value is requested, such as where the value is small or hex does not make sense in the context. In these cases it is sometimes useful to be able to provide a hex value in any case, if only to resolve any ambiguity. Add this functionality, for increased flexibility. Signed-off-by: Simon Glass <sjg@chromium.org>
93 lines
2.8 KiB
ReStructuredText
93 lines
2.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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Command-line Parsing
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====================
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The command line is available in U-Boot proper, enabled by CONFIG_CMDLINE which
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is on by default. It is not enabled in SPL.
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There are two different command-line parsers available with U-Boot:
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the old "simple" one, and the much more powerful "hush" shell:
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Simple command-line parser
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--------------------------
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This takes very little code space and offers only basic features:
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- supports environment variables (through setenv / saveenv commands)
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- several commands on one line, separated by ';'
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- variable substitution using "... ${name} ..." syntax
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- special characters ('$', ';') can be escaped by prefixing with '\',
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for example::
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setenv bootcmd bootm \${address}
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- You can also escape text by enclosing in single apostrophes, for example::
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setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
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Hush shell
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----------
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This is similar to Bourne shell, with control structures like:
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- `if`... `then` ... `else`... `fi`
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- `for`... `do` ... `done`
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- `while` ... `do` ... `done`
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- `until` ... `do` ... `done`
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Hush supports environment ("global") variables (through setenv / saveenv
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commands) and local shell variables (through standard shell syntax
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`name=value`); only environment variables can be used with the "run" command
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The Hush shell is enabled with `CONFIG_HUSH_PARSER`.
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General rules
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-------------
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#. If a command line (or an environment variable executed by a "run"
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command) contains several commands separated by semicolon, and
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one of these commands fails, then the remaining commands will be
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executed anyway.
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#. If you execute several variables with one call to run (i. e.
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calling run with a list of variables as arguments), any failing
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command will cause "run" to terminate, i. e. the remaining
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variables are not executed.
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Representing numbers
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--------------------
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Most U-Boot commands use hexadecimal (hex) as the default base, for convenient
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use of addresses, for example::
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=> md 1000 6
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00001000: 2c786f62 00697073 03000000 0c000000 box,spi.........
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00001010: 67020000 00000000 ...g....
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There is no need to add a `0x` prefix to the arguments and the output is shown
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in hex also, without any prefixes. This helps to avoid clutter.
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Some commands use decimal where it is more natural::
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=> i2c dev 0
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Setting bus to 0
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=> i2c speed
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Current bus speed=400000
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=> i2c speed 100000
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Setting bus speed to 100000 Hz
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In some cases the default is decimal but it is possible to use octal if that is
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useful::
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pmic dev pmic@41
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dev: 1 @ pmic@41
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=> pmic write 2 0177
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=> pmic read 2
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0x02: 0x00007f
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It is possible to use a `0x` prefix to use a hex value if that is more
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convenient::
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=> i2c speed 0x30000
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Setting bus speed to 196608 Hz
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