Raspberry Pi 5 fails to boot with a large config.txt

[leon-anavi]

Is this the right place for my bug report?

Yes, because it is related to the boot process and config.txt size.

Describe the bug

While adding Raspberry Pi 5 support in Yocto/OpenEmbedded BSP meta-raspberrypi we noticed that the board doesn't boot with a large config.txt file: agherzan/meta-raspberrypi#1237

I haven't seen this issue before on previous Raspberry Pi models and versions. @floion started a discussion in the Raspberry Pi forum. jamesh, Raspberry Pi Engineer & Forum Moderator, recommended to get rid of the comments and reduce the file size. In meta-raspberrypi we can do this easily with sed -i '/^##/d' $CONFIG (at least temporary until we have a better solution) but let's also report the issue here too.

To reproduce

Try booting Raspberry Pi 5 with a large config.txt: https://raw.githubusercontent.com/Evilpaul/RPi-config/master/config.txt

Expected behaviour

The expected behavior is Raspberry Pi 5 to boot.

Actual behaviour

Raspberry Pi 5 doesn't boot.

System
Copy and paste the results of the raspinfo command in to this section. Alternatively, copy and paste a pastebin link, or add answers to the following questions:

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW

Raspberry Pi 5

• Which OS and version (cat /etc/rpi-issue)?

Raspberry Pi OS or image built with agherzan/meta-raspberrypi#1237

• Which firmware version (vcgencmd version)?
• Which kernel version (uname -a)?

Logs
If applicable, add the relevant output from dmesg or similar.

raspberrypi5-large-config-20231124.txt

Additional context

[timg236]

Edit: The limit for a single config.txt file or include is 16K. There's no need to support arbitrarily large config.txt files.

[leon-anavi]

@timg236 thank you for the quick feedback and the shared technical details. Noted down. In the particular case config.txt is 49K so your explanation makes sense:

$ ls -lah config.txt
-rw-r--r-- 1 leon leon 49K ное 24 13:55 config.txt

Regarding these circumstances in short term at Yocto/OpenEmbedded BSP layer meta-raspbebrrypi we will just remove various comments from config.txt to reduce the file size and in long term we will come up with more sustainable solution for config.txt.

[timg236]

For larger config.txt files using include statements may be helpful. I think there's possibly room for improvement with error messages in future bootloader updates so we can add that to the backlog.
Amongst other reasons the bounded size is that config.txt is now parsed earlier by the bootloader code which is has a bounded size for signature checks