Commit 8c249290 authored by Karsten Merker's avatar Karsten Merker Committed by Tom Rini
Browse files

Document config_distro_bootcmd environment variables for interactive booting.

config_distro_bootcmd.h defines a common boot environment for multiple
platforms, including several environment variables that are intended for
interactive use by an end-user.  Document which variables are considered
public interfaces that must remain compatible in future u-boot versions.
Signed-off-by: default avatarKarsten Merker <>
Acked-by: Stephen Warren's avatarStephen Warren <>
parent 1344bd7e
* (C) Copyright 2014 Red Hat Inc.
* Copyright (c) 2014-2015, NVIDIA CORPORATION. All rights reserved.
* Copyright (C) 2015 K. Merker <>
* SPDX-License-Identifier: GPL-2.0+
......@@ -339,3 +340,49 @@ scan_dev_for_scripts:
If you want to disable boot.scr on all disks, set the value to something
innocuous, e.g. setenv scan_dev_for_scripts true.
Interactively booting from a specific device at the u-boot prompt
For interactively booting from a user-selected device at the u-boot command
prompt, the environment provides predefined bootcmd_<target> variables for
every target defined in boot_targets, which can be run be the user.
If the target is a storage device, the format of the target is always
<device type><device number>, e.g. mmc0. Specifying the device number is
mandatory for storage devices, even if only support for a single instance
of the storage device is actually implemented.
For network targets (dhcp, pxe), only the device type gets specified;
they do not have a device number.
- run bootcmd_usb0
boots from the first USB mass storage device
- run bootcmd_mmc1
boots from the second MMC device
- run bootcmd_pxe
boots by tftp using a pxelinux.cfg
The list of possible targets consists of:
- network targets
* dhcp
* pxe
- storage targets (to which a device number must be appended)
* mmc
* sata
* scsi
* ide
* usb
Other *boot* variables than the ones defined above are only for internal use
of the boot environment and are not guaranteed to exist or work in the same
way in future u-boot versions. In particular the <device type>_boot
variables (e.g. mmc_boot, usb_boot) are a strictly internal implementation
detail and must not be used as a public interface.
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