On Wed, Sep 5, 2018 at 3:36 PM Frank Rowand [off-list ref] wrote:

+cc: devicetree-compiler at vger.kernel.org

     For context on the device-tree compiler list, this patch is for
     the Linux kernel.

On 09/04/18 01:05, Tero Kristo wrote:

quoted

Add simple support for building DT overlays. This just compiles any
given .dtso file under the base arch/arm/boot/dts directory into
a .dtbo.

Signed-off-by: Tero Kristo <redacted>
---
 arch/arm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index d1516f8..ab555a0 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile

@@ -339,7 +339,7 @@ $(BOOT_TARGETS): vmlinux
 $(INSTALL_TARGETS):
      $(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@

-%.dtb: | scripts
+%.dtb %.dtbo: | scripts

This will need to change with my rework of the DT build rules[1].

quoted

      $(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@

 PHONY += dtbs dtbs_install

The idea of adding knowledge of .dtso and .dtbo files to the dtc
compiler, but that idea and the related patches have fallen by
the wayside.

Current overlay sources and blobs are properly handled by dtc when
they are .dts and .dtb files.

If the dtc compiler is updated with knowledge of .dtso and .dtbo
then these changes would be needed.  At the moment the distinction
of a .dtso and .dtbo is a naming convention that provides a clue
about the intended use of the file.  But dtc does not know these
file name extensions, requiring a specific flag to tell dtc to
treat them as .dts or .dtb files.  I think the negative outweighs
the positive for this patch.

I don't follow what you are proposing. We should decide on a convention though.

We shouldn't need .dtso because that is identified with the /plugin/
tag. Distinguishing overlay dtbs with .dtbo seems like a good idea
though.

Rob

[1] https://lkml.org/lkml/2018/8/21/770