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Device tree compiler binary #311

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Device tree compiler binary #311

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Lucassifoni
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Hello,

This is a draft that I will enhance with details as I make some progress.

I've seen that mount -t configfs none /sys/kernel/config makes the /sys/kernel/config/device-tree/overlays folder appear on this stock raspbian : Linux raspberrypi 4.19.97-v7+ #1294 SMP Thu Jan 30 13:15:58 GMT 2020 armv7l GNU/Linux Raspbian GNU/Linux 10 (buster).

In its current state, this PR adds the dtc binary via BR2_PACKAGE_DTC_PROGRAMS.

It also adds CONFIG_OF_OVERLAY=y, but :

  • this doesn't solve the problem
  • I then learned that this directive is auto-included if CONFIG_OF_CONFIGFS=y is included.

So I'm trying various things to make progress. Thought I'd open the PR to see if someone has an idea.

@Lucassifoni
Add BR2_PACKAGE_DTC_PROGRAMS=y to nerves_defconfig
db1adf6 
See : https://github.com/buildroot/buildroot/blob/master/package/dtc/Config.in 

```
config BR2_PACKAGE_DTC_PROGRAMS
	bool "dtc programs"
	help
	  Say 'y' here if you also want the programs on the target:
	    - convert-dtsv0     convert from version 0 to version 1
	    - dtc               the device tree compiler
	    - dtdiff            compare two device trees (needs bash)
	    - fdtdump           print a readable version of a
	                        flat device tree
	    - fdtget            read values from device tree
	    - fdtput            write a property value to a device tree
```
@Lucassifoni
Update linux-6.1.defconfig to add CONFIG_OF_OVERLAY=y
bd639f8
@fhunleth
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The official Raspberry Pi way is to load overlays via the dtoverlay command. Its source is at https://github.com/raspberrypi/userland/tree/master/host_applications/linux/apps/dtoverlay. dtoverlay is included in the system and should work. I tested it on other Raspberry Pis. CONFIG_OF_OVERLAY=y isn't needed here since OF_CONFIGFS=y selects it. (This isn't obvious unless you read kernel source or run make linux-menuconfig and look.)

Enabling BR2_PACKAGE_DTC_PROGRAMS=y to compile and load overlays without dtoverlay seems like a good change to me, fwiw.

@Lucassifoni
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@fhunleth sorry for the lost time. I don't know what exactly failed in my last test, but on-device compilation & loading of an overlay worked this morning, just with the DTC_PROGRAMS line. So I'm resuming work on the DTS loader assistant :^).

@Lucassifoni Lucassifoni marked this pull request as ready for review February 2, 2024 09:32
@Lucassifoni Lucassifoni changed the title [WIP] Device tree compiler and support for configfs Device tree compiler binary Feb 2, 2024
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@Lucassifoni @fhunleth