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Description
Describe the bug
If I set dtoverlay=uart3 in /boot/config.txt on a Raspberry Pi 4 and reboot, /dev/ttyAMA3 exists. If I don't set dtoverlay=uart3 in /boot/config.txt and instead run dtoverlay uart3, no /dev/ttyAMA3 appears.
This is different from how other overlays work. For example, running dtoverlay spi0-1cs causes /dev/spidev0.0 to appear immediately, similar to how it exists after a reboot when instead setting dtoverlay=spi0-1cs in /boot/config.txt.
A similar issue has been mentioned in https://raspberrypi.stackexchange.com/questions/143151/pi4-enable-uart4-without-using-boot-config-txt, but I was unable to find a solution.
Steps to reproduce the behaviour
- Ensure there are no
dtoverlay=uart*entries in/boot/config.txt - Run
dtoverlay uart3 - Check whether a corresponding
/dev/ttyAMA3exists
Device (s)
Raspberry Pi 4 Mod. B
System
Arch Linux ARM
$ vcgencmd version
May 14 2025 12:23:36
Copyright (c) 2012 Broadcom
version 17084b403fb60475b8ee2641c26049a7d54bf153 (clean) (release) (start)
$ uname -a
Linux rpi 6.12.43-1-rpi #1 SMP PREEMPT Tue Aug 26 13:22:07 MDT 2025 aarch64 GNU/Linux
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