Re: [Buildroot] Adding Device Tree Overlays for MIPI-CSI2 Camera and libcamera to a buildroot Build

[buildroot@cairnwater.com]

Hi Fiona,

Thank you very much! That's a big help to know to use 
BR2_LINUX_KERNEL_CUSTOM_DTS_DIR for that.

What directory structure is needed for the overlays? Just the DTO files 
in a directory or something more complicated?

> From there you'll need to adjust the boot process for your board to 
> actually apply the overlay. If you want to send a patch, the 
> BR2_LINUX_KERNEL_CUSTOM_DTS_DIR should be inside the board directory.

Thank you very much. I don't know how to do that. What's the best way to 
get the boot process to apply the overlay? I'd heard that it can be done 
by the kernel or by U-Boot but I'm doing this for the first time so I'm 
not sure what I'm doing.

Will


On 2025-05-07 17:41, Fiona Klute via buildroot wrote:
> Hi Will!
> 
> Am 07.05.25 um 17:41 schrieb buildroot@cairnwater.com:
>> Does anyone have any advice on how to add DTOs needed by libcamera to 
>> a buildroot build?
>> 
>> We'd like to add Kieran's DTOs
>> 
>> https://git.uk.ideasonboard.com/camera/dt-overlays/src/branch/main/arch/ 
>> arm64/boot/dts/freescale
>> 
>> to the buildroot default configuration for Debix Model A SBC
>> 
>> https://github.com/buildroot/buildroot/blob/master/configs/ 
>> polyhex_debix_model_a_defconfig
>> 
>> Ideally we'd also like to add the overlays for the Sony IMX 708 Image 
>> Sensor used in the RPi V3 camera but these aren't mainline:
>> 
>> https://github.com/raspberrypi/linux/blob/rpi-6.12.y/arch/arm/boot/dts/ 
>> overlays/imx708-overlay.dts
>> https://github.com/raspberrypi/linux/blob/rpi-6.12.y/arch/arm/boot/dts/ 
>> overlays/imx708.dtsi
> 
> You can use BR2_LINUX_KERNEL_CUSTOM_DTS_DIR for that: Just place the 
> DTSOs in the configured directory (with appropriate structure), and 
> Buildroot will build them automatically. DTBOs will be in 
> ${OUTPUT_DIR}/images. From there you'll need to adjust the boot process 
> for your board to actually apply the overlay. If you want to send a 
> patch, the BR2_LINUX_KERNEL_CUSTOM_DTS_DIR should be inside the board 
> directory.
> 
> With RPi overlays you'll probably have to adjust the overlays a bit so 
> referenced names fit, etc. You're using a different board, and I've 
> seen cases where DTS for RPi boards from mainline and RPi kernels use 
> different names. But that doesn't change the build process. :-)
> 
> Best regards,
> Fiona
> 
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