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| -rw-r--r-- | doc/README.distro | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/doc/README.distro b/doc/README.distro index dd0f1c7b6af..0308a4c73ab 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 <merker@debian.org> * * 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. + +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 <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. |