display_auto_detect is enabled by default in the config.txt file supplied with bookworm.

$ grep display_auto_detect /boot/firmware/config.txt 
display_auto_detect=1

It is not set by default in the bootloader/firmware.

This behaviour does not come from the kernel and it's by design.

Ok.... but then I think the documentation is not entirely clear: you state that it is by default available in the config.txt provided by bookworm, but the documention does not mention a specific distribution anywhere. The only thing that is stated is this:

Auto detect

Auto detect allows your Raspberry Pi to connect with a display without a manually configured device tree overlay. Auto detection is enabled by default. You can enable display auto detect by adding the following line to config.txt:

I've transferred this to the documentation repo issues.

For clarity the behaviour is:
bootloader/firmware defaults display_auto_detect to 0.
Default bookworm config.txt include display_auto_detect=1 to make feature enabled by default on bookworm.

camera_auto_detect behaves the same.

the documention does not mention a specific distribution anywhere.

The entirety of https://www.raspberrypi.com/documentation/ is written to target the latest version of Raspberry Pi OS. If you're using a 3rd-party OS, then you'll have to check the documentation for that other OS.

@nathan-contino Similar questions / issues have cropped up before, so perhaps this should be explicitly stated in https://github.com/raspberrypi/documentation/blob/develop/README.md ?

I agree the current wording is imprecise:

Enabled by default.

When enabled, the firmware will automatically load overlays for recognised DSI displays.

To disable, set display_auto_detect=0.

As a config.txt option (where this is being documented) it is not enabled by default.
To disable it you just remove the line (display_auto_detect=0 is a no-op).

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.