U-Boot: extlinux.conf boot menu support appears to be broken by commit 739e8361f3fe78038251216df6096a32bc2d5839

[Karsten Merker]

Hello,

it looks like the following commit has broken the extlinux.conf
boot menu support in U-Boot:

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commit 739e8361f3fe78038251216df6096a32bc2d5839
Author: Manuel Traut <manuel.traut at mt.com>
Date:   Fri Nov 18 09:00:27 2022 +0100

    distro/pxeboot: Handle prompt variable
    
    Regarding the documentation found here:
    https://github.com/u-boot/u-boot/blob/master/common/menu.c#L347
    
    If both timeout and prompt is set to 0 the default entry shall
    be booted immediately. However the current behaviour is that
    the prompt is shown (tested with distroboot) until the user
    selects an entry (no timeout).
    
    This change implements a behaviour as documented. It was tested
    with distroboot.
    
    Signed-off-by: Manuel Traut <manuel.traut at mt.com>
    Reviewed-by: Simon Glass <sjg at chromium.org>
    Reviewed-by: Simon Glass <sjg at chromium.org>
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Since the commit above, a system with the following
/boot/extlinux/extlinux.conf (which sets timeout to 50)
immediately boots the first entry in the config without
displaying a boot menu.  According to the description, that
should only happen if both prompt and timeout are set to zero in
the config, but it also happens with timeout set to a non-zero
value as in the config below:

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## /boot/extlinux/extlinux.conf
##
## IMPORTANT WARNING
##
## The configuration of this file is generated automatically.
## Do not edit this file manually, use: u-boot-update

default l0
menu title U-Boot menu
prompt 0
timeout 50


label l0
	menu label Debian GNU/Linux bookworm/sid 6.1.0-1-riscv64
	linux /boot/vmlinux-6.1.0-1-riscv64
	initrd /boot/initrd.img-6.1.0-1-riscv64
	
	
	append root=/dev/vda1 rw noquiet

label l0r
	menu label Debian GNU/Linux bookworm/sid 6.1.0-1-riscv64 (rescue target)
	linux /boot/vmlinux-6.1.0-1-riscv64
	initrd /boot/initrd.img-6.1.0-1-riscv64
	
	append root=/dev/vda1 rw noquiet single
	

label l1
	menu label Debian GNU/Linux bookworm/sid 6.0.0-6-riscv64
	linux /boot/vmlinux-6.0.0-6-riscv64
	initrd /boot/initrd.img-6.0.0-6-riscv64
	
	
	append root=/dev/vda1 rw noquiet

label l1r
	menu label Debian GNU/Linux bookworm/sid 6.0.0-6-riscv64 (rescue target)
	linux /boot/vmlinux-6.0.0-6-riscv64
	initrd /boot/initrd.img-6.0.0-6-riscv64
	
	append root=/dev/vda1 rw noquiet single
	

label l2
	menu label Debian GNU/Linux bookworm/sid 6.0.0-5-riscv64
	linux /boot/vmlinux-6.0.0-5-riscv64
	initrd /boot/initrd.img-6.0.0-5-riscv64
	
	
	append root=/dev/vda1 rw noquiet

label l2r
	menu label Debian GNU/Linux bookworm/sid 6.0.0-5-riscv64 (rescue target)
	linux /boot/vmlinux-6.0.0-5-riscv64
	initrd /boot/initrd.img-6.0.0-5-riscv64
	
	append root=/dev/vda1 rw noquiet single
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Up to commit 51c5c28af59c19407d6602336ac7374dd1432c49 the boot process
with the extlinux.conf above looks as follows:

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Hit any key to stop autoboot:  0 

Device 0: QEMU VirtIO Block Device
            Type: Hard Disk
            Capacity: 102400.0 MB = 100.0 GB (209715200 x 512)
... is now current device
Scanning virtio 0:1...
Found /boot/extlinux/extlinux.conf
Retrieving file: /boot/extlinux/extlinux.conf
U-Boot menu
1:	Debian GNU/Linux bookworm/sid 6.1.0-1-riscv64
2:	Debian GNU/Linux bookworm/sid 6.1.0-1-riscv64 (rescue target)
3:	Debian GNU/Linux bookworm/sid 6.0.0-6-riscv64
4:	Debian GNU/Linux bookworm/sid 6.0.0-6-riscv64 (rescue target)
5:	Debian GNU/Linux bookworm/sid 6.0.0-5-riscv64
6:	Debian GNU/Linux bookworm/sid 6.0.0-5-riscv64 (rescue target)
Enter choice:    
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The user can then either select a boot menu entry or - if there is
no user input - the system boots the first entry after the timeout
set in extlinux.conf is over.

Starting with commit 739e8361f3fe78038251216df6096a32bc2d5839,
the boot process looks as follows, i.e. there isn't a boot menu
anymore but the system immediately boots the first entry:

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Device 0: QEMU VirtIO Block Device
            Type: Hard Disk
            Capacity: 102400.0 MB = 100.0 GB (209715200 x 512)
... is now current device
Scanning virtio 0:1...
Found /boot/extlinux/extlinux.conf
Retrieving file: /boot/extlinux/extlinux.conf
1:	Debian GNU/Linux bookworm/sid 6.1.0-1-riscv64
Retrieving file: /boot/vmlinux-6.1.0-1-riscv64
Retrieving file: /boot/initrd.img-6.1.0-1-riscv64
append: root=/dev/vda1 rw noquiet
Moving Image from 0x84000000 to 0x80200000, end=815e5000
## Flattened Device Tree blob at ff7344b0
   Booting using the fdt blob at 0xff7344b0
Working FDT set to ff7344b0
   Using Device Tree in place at 00000000ff7344b0, end 00000000ff738dea
Working FDT set to ff7344b0

Starting kernel ...
[...]
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Regards,
Karsten
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