From 8c2492901998a76e083ed0875372c141da084d86 Mon Sep 17 00:00:00 2001 From: Karsten Merker Date: Sat, 21 Mar 2015 14:15:38 +0100 Subject: 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: Karsten Merker Acked-by: Stephen Warren --- doc/README.distro | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'doc') diff --git a/doc/README.distro b/doc/README.distro index dd0f1c7..0308a4c 100644 --- a/doc/README.distro +++ b/doc/README.distro @@ -1,6 +1,7 @@ /* * (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_ 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 +, 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. + +Examples: + + - 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 _boot +variables (e.g. mmc_boot, usb_boot) are a strictly internal implementation +detail and must not be used as a public interface. -- cgit v1.1