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I am trying to build a device-tree overlay using DKMS for a running kernel (4.4). My naive Makefile is as follows:

PWD := $(shell pwd)

dtbo-y += my-awsome-overlay.dtbo
targets += $(dtbo-y)

all:
        make -C /lib/modules/${kernelver}/build M=$(PWD) dtbs

clean:
        make -C /lib/modules/${kernelver}/build M=$(PWD) clean

However, I am getting the following error:

make[1]: Entering directory '/usr/src/linux-headers-4.4.13-v7+'
/bin/sh: 1: cannot create arch/arm/boot/dts/overlays/modules.order: Permission denied

How can I fix it? It should be possible without root privileges, right?

How would a standard Makefile for building dt overlays using DKMS look like?

Edit: I think I have solved the problem, see below. However, a qualified answer would still be welcome.

sergej
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1 Answers1

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  1. Change my-awsome-overlay.dtbo to my-awsome.dtbo. Assuming the dts file name is my-awsome-overlay.dts.

  2. Add always := $(dtbo-y).

  3. Invoke make without a target (remove dtbs).

Here is a working Makefile:

PWD := $(shell pwd)

dtbo-y += my-awsome.dtbo

targets += $(dtbo-y)    
always  := $(dtbo-y)

all:
        make -C /lib/modules/${kernelver}/build M=$(PWD)

clean:
        make -C /lib/modules/${kernelver}/build M=$(PWD) clean
sergej
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  • Would be awesome to see the dkms.conf for an overlay as well. – ensonic Nov 22 '16 at 12:44
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    @ensonic see here: https://github.com/taudac/taudac-driver-dkms/blob/overlay/dkms.conf – sergej Nov 22 '16 at 19:08
  • I think this will only work on the Rasp Pi kernels, is that right? I'd be interested in solving this for stock (or Debian) kernels as well. Still, thanks for this as a hint on how to get started! – Jarrad Jan 08 '22 at 22:56