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doc:bootmenu: add description for UEFI boot support

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The bootmenu enumerates the UEFI boot options
for boot device selection.
This commit adds the description how the UEFI boot work
in bootmenu. This commit also adds "Synopsis", "Description"
and "Configuration" sections to follow the U-Boot command
documentation format.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This commit is contained in:
Masahisa Kojima 2022-09-12 17:33:57 +09:00 committed by Heinrich Schuchardt
parent e5948ee301
commit f076c994bf
1 changed files with 74 additions and 0 deletions
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74
doc/usage/cmd/bootmenu.rst
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@ -4,6 +4,15 @@
bootmenu command
================
Synopsis
--------
::
bootmenu [delay]
Description
-----------
The "bootmenu" command uses U-Boot menu interfaces and provides
a simple mechanism for creating menus with different boot items.
The cursor keys "Up" and "Down" are used for navigation through
@ -79,6 +88,55 @@ The above example will be rendered as below::
The selected menu entry will be highlighted - it will have inverted
background and text colors.
UEFI boot variable enumeration
''''''''''''''''''''''''''''''
If enabled, the bootmenu command will automatically generate and add
UEFI-related boot menu entries for the following items.
* possible bootable media with default file names
* user-defined UEFI boot options
The bootmenu automatically enumerates the possible bootable
media devices supporting EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.
This auto generated entry is named as "<interface> <devnum>:<part>" format.
(e.g. "usb 0:1")
The bootmenu displays the UEFI-related menu entries in order of "BootOrder".
When the user selects the UEFI boot menu entry, the bootmenu sets
the selected boot variable index to "BootNext" without non-volatile attribute,
then call the uefi boot manager with the command "bootefi bootmgr".
Example bootmenu is as below::
*** U-Boot Boot Menu ***
mmc 0:1
mmc 0:2
debian
nvme 0:1
ubuntu
nvme 0:2
usb 0:2
U-Boot console
Default behavior when user exits from the bootmenu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
User can exit from bootmenu by selecting the last entry
"U-Boot console"/"Quit" or ESC/CTRL+C key.
When the CONFIG_BOOTMENU_DISABLE_UBOOT_CONSOLE is disabled,
user exits from the bootmenu and returns to the U-Boot console.
When the CONFIG_BOOTMENU_DISABLE_UBOOT_CONSOLE is enabled, user can not
enter the U-Boot console. When the user exits from the bootmenu,
the bootmenu invokes the following default behavior.
* if CONFIG_CMD_BOOTEFI_BOOTMGR is enabled, execute "bootefi bootmgr" command
* "bootefi bootmgr" fails or is not enabled, then execute "run bootcmd" command.
Configuration
-------------
The "bootmenu" command is enabled by::
CONFIG_CMD_BOOTMENU=y
@ -88,3 +146,19 @@ To run the bootmenu at startup add these additional settings::
CONFIG_AUTOBOOT_KEYED=y
CONFIG_BOOTDELAY=30
CONFIG_AUTOBOOT_MENU_SHOW=y
UEFI boot variable enumeration is enabled by::
CONFIG_CMD_BOOTEFI_BOOTMGR=y
To improve the product security, entering U-Boot console from bootmenu
can be disabled by::
CONFIG_BOOTMENU_DISABLE_UBOOT_CONSOLE=y
To scan the discoverable devices connected to the buses such as
USB and PCIe prior to bootmenu showing up, CONFIG_PREBOOT can be
used to run the command before showing the bootmenu, i.e.::
CONFIG_USE_PREBOOT=y
CONFIG_PREBOOT="pci enum; usb start; scsi scan; nvme scan; virtio scan"