Bug#1091979: u-boot-menu: Fails to add fdt or fdtdir entries

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Johannes Schauer Marin Rodrigues

2025-01-02 23:00:01 UTC

Package: u-boot-menu
Version: 4.2.3
Severity: normal

Hi,

I installed Debian Trixie on my MNT Reform with imx8mq with separate /boot
partition and a snippet from the resulting /boot/extlinux/extlinux.conf looks
like this:

default l0
menu title U-Boot menu
prompt 1
timeout 50

label l0
menu label Debian GNU/Linux trixie/sid 6.12.6-mnt-reform-arm64
linux /vmlinuz-6.12.6-mnt-reform-arm64
initrd /initrd.img-6.12.6-mnt-reform-arm64

append ro no_console_suspend cryptomgr.notests loglevel=3 ${bootargs} console=tty1

The lines that should contain an fdt or fdtdir entry are missing. Lets look at
the sh -x output to figure out why they were not generated:

1 P: Writing config for vmlinuz-6.12.6-mnt-reform-arm64...
2 + _NUMBER=0
3 + _ENTRY=1
4 + [ -e /boot/initrd.img-6.12.6-mnt-reform-arm64 ]
5 + _INITRD=initrd /initrd.img-6.12.6-mnt-reform-arm64
6 + [ -e ]
7 + [ -e /boot6.12.6-mnt-reform-arm64/ ]
8 + [ -d /boot6.12.6-mnt-reform-arm64/ ]
9 + [ -f /boot/dtb-6.12.6-mnt-reform-arm64 ]
10 + [ /usr/lib/linux-image- = ]
11 + _FDT=

Line 6 checks an empty value because U_BOOT_FDT is unset. Line 7 and 8 cannot
work because there is a missing slash between ${_BOOT_PATH} and
${U_BOOT_FDT_DIR}. Line 9 finds /boot/dtb-6.12.6-mnt-reform-arm64 but the check
in line 10 fails because {U_BOOT_FDT_DIR} is unset. Why is it unset? Because
even though read-config found a separate /boot partition in
has_separate_boot(), U_BOOT_SYNC_DTBS was set to false, so _FDT_DIR was never
set to "/dtb-" and even if it were set to that, the check in line 10 would
still fail because "/usr/lib/linux-image-" is not equal to "/dtb-". So to
summarize:

1. why is a fdt or fdtdir line not added by default?
2. why are there missing slashes in line 7 and 8?
3. why do i have to enable U_BOOT_SYNC_DTBS? I already use flash-kernel for that
4. why is there a check for "/usr/lib/linux-image-" if _FDT_DIR gets set to "/dtb-"?

One workaround is to set:

U_BOOT_FDT_DIR="/dtbs/"

which will then add fdtdir entries that look correct. The slashes are critical
because they are missing in the u-boot-update script.

Thanks!

cheers, josch

Johannes Schauer Marin Rodrigues

2025-03-03 08:20:01 UTC

Permalink

Hi,

Quoting Johannes Schauer Marin Rodrigues (2025-01-02 23:53:53)

Post by Johannes Schauer Marin Rodrigues
The lines that should contain an fdt or fdtdir entry are missing. Lets look at
1 P: Writing config for vmlinuz-6.12.6-mnt-reform-arm64...
2 + _NUMBER=0
3 + _ENTRY=1
4 + [ -e /boot/initrd.img-6.12.6-mnt-reform-arm64 ]
5 + _INITRD=initrd /initrd.img-6.12.6-mnt-reform-arm64
6 + [ -e ]
7 + [ -e /boot6.12.6-mnt-reform-arm64/ ]
8 + [ -d /boot6.12.6-mnt-reform-arm64/ ]
9 + [ -f /boot/dtb-6.12.6-mnt-reform-arm64 ]
10 + [ /usr/lib/linux-image- = ]
11 + _FDT=
Line 6 checks an empty value because U_BOOT_FDT is unset. Line 7 and 8 cannot
work because there is a missing slash between ${_BOOT_PATH} and
${U_BOOT_FDT_DIR}. Line 9 finds /boot/dtb-6.12.6-mnt-reform-arm64 but the check
in line 10 fails because {U_BOOT_FDT_DIR} is unset. Why is it unset? Because
even though read-config found a separate /boot partition in
has_separate_boot(), U_BOOT_SYNC_DTBS was set to false, so _FDT_DIR was never
set to "/dtb-" and even if it were set to that, the check in line 10 would
still fail because "/usr/lib/linux-image-" is not equal to "/dtb-". So to
1. why is a fdt or fdtdir line not added by default?
2. why are there missing slashes in line 7 and 8?
3. why do i have to enable U_BOOT_SYNC_DTBS? I already use flash-kernel for that
4. why is there a check for "/usr/lib/linux-image-" if _FDT_DIR gets set to "/dtb-"?
U_BOOT_FDT_DIR="/dtbs/"
which will then add fdtdir entries that look correct. The slashes are critical
because they are missing in the u-boot-update script.

so here is a potential patch:

--- /usr/share/u-boot-menu/read-config
+++ /usr/share/u-boot-menu/read-config
@@ -48,6 +48,8 @@
if [ "${U_BOOT_SYNC_DTBS}" = "true" ]
then
_FDT_DIR="/dtb-"
+ else
+ _FDT_DIR="/dtbs/"
fi
else
# / and /boot are on the same filesystem

With that in place, extlinux.conf will now contain a line like this:

fdtdir /dtbs/6.12.15-mnt-reform-arm64/

Note, how this is still a change in behaviour. With u-boot-menu from Bookworm,
not fdtdir would be set but one would have:

fdt /dtb-6.12.15-mnt-reform-arm64

But maybe that change is intentional?

I can make an attempt at different fix for this problem but I'd need to
understand what is supposed to happen first. My four questions above still are
unanswered and especially with the missing slashes and the unset _FDT_DIR, the
code *can* not work as it is or am I missing something?

Thanks!

cheers, josch

Vagrant Cascadian

2025-03-03 18:00:01 UTC

Permalink

Looping Arnaud into the conversation, as I suspect the patches submitted
were touching this code quite a bit:

51d120d549e5b21a19ce659c7bef578c86ed9636 Allow to automatically sync DTBs when /boot is on a separate partition (Closes: #1025956)
96a866bc886f118de9286a00587b2e1fcf263105 read-config: make /boot partition check a function

Of course I am the one who uploaded them, but antoehr pair of eyes
obviously will not hurt! :)

live well,
vagrant

Post by Johannes Schauer Marin Rodrigues
Quoting Johannes Schauer Marin Rodrigues (2025-01-02 23:53:53)

--- /usr/share/u-boot-menu/read-config
+++ /usr/share/u-boot-menu/read-config
@@ -48,6 +48,8 @@
if [ "${U_BOOT_SYNC_DTBS}" = "true" ]
then
_FDT_DIR="/dtb-"
+ else
+ _FDT_DIR="/dtbs/"
fi
else
# / and /boot are on the same filesystem
fdtdir /dtbs/6.12.15-mnt-reform-arm64/
Note, how this is still a change in behaviour. With u-boot-menu from Bookworm,
fdt /dtb-6.12.15-mnt-reform-arm64
But maybe that change is intentional?
I can make an attempt at different fix for this problem but I'd need to
understand what is supposed to happen first. My four questions above still are
unanswered and especially with the missing slashes and the unset _FDT_DIR, the
code *can* not work as it is or am I missing something?
Thanks!
cheers, josch