[PATCH v6 5/6] doc:bootmenu: add description for UEFI boot support

[Masahisa Kojima]

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 at linaro.org>
---
Changes in v6:
- remove distro boot related contents because the distro boot
support in bootmenu is dropped
- update uefi entry example
- add [delay] argument of bootmenu command
- add description to enable uefi boot entry

Changes in v5:
- follow the cmd documentation format same as other command, add "Synopsis",
  "Description" add "Configuration" sections

Newly created in v4

 doc/usage/cmd/bootmenu.rst | 55 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/doc/usage/cmd/bootmenu.rst b/doc/usage/cmd/bootmenu.rst
index 9430f8c9aa..6b154d9655 100644
--- a/doc/usage/cmd/bootmenu.rst
+++ b/doc/usage/cmd/bootmenu.rst
@@ -4,6 +4,16 @@
 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 +89,35 @@ 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
+''''''''''''''''''''''''''''''
+
+The bootmenu automatically generates the UEFI boot variable("BOOT####")
+in order of "BootOrder". When the user selects the UEFI boot
+variable entry, bootmenu sets the selected boot variable index
+to "BootNext", then call the uefi boot manager with the command
+"bootefi bootmgr".
+
+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")
+
+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
+
+Configuration
+-------------
+
 The "bootmenu" command is enabled by::
 
     CONFIG_CMD_BOOTMENU=y
@@ -88,3 +127,19 @@ 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_AUTOBOOT_MENU_SHOW=y
+
+To improve the product security, entering U-Boot console from bootmenu
+can be disabled by::
+
+    CONFIG_CMD_BOOTMENU_ENTER_UBOOT_CONSOLE=n
+
+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"
-- 
2.17.1