Specifying more than one DT overlay in the uEnv.txt file

General Discussion
1

Hi all!
Am using the BBB Debian 11 kernel ver is 5.10.168-ti-r71, booting off the uSD card.

I find using DT overlays very useful - i just set them up in the /boot/uEnv.txt and it loads up (via U-Boot)… However, what if I want to load more than one DT overlay? For example, I put these 2 lines in my uEnv.txt:

...
dtb_overlay=/boot/dtbs/5.10.168-ti-r71/overlays/BBB-TESTOVERLAY.dtbo
dtb_overlay=/boot/dtbs/5.10.168-ti-r71/overlays/BBB-DHT2X.dtbo

I find that only the last one specified is actually loaded by U-Boot… Also, they don’t clash in any way. (Also, fyi, i don’t find any extlinux.conf in my setup).
Any help appreciated!

TIA, Kaiwan

2

The syntax is not correct, should be something like below.

copied from my BBB uEnv.txt. Obviously need to un-comment the lines and put in the correct filenames.

###Additional custom capes
#uboot_overlay_addr4=<file4>.dtbo
#uboot_overlay_addr5=<file5>.dtbo
#uboot_overlay_addr6=<file6>.dtbo
#uboot_overlay_addr7=<file7>.dtbo
###
3

Thanks @benedict.hewson !

I also just happened to come across this solution in this nice article:
The Beaglebone Black and Device Tree Overlays

As well, as mentioned there, we can use the

### Custom cape
dtb_overlay=<...>

line to get one more, so in effect, looks like one can specify upto 5 DTB overlays at a time (and they shouldn’t conflict of course)… 4 in the uboot_overlay_addr[4-7] and one via dtb_overlay

4

and uboot_overlay_addr[0-3] as it’ll just override the ‘auto’ detect…

Regards,