Hi Mark,
That is extremely helpful - thank you for the quick and comprehensive response
:). More comments below...
>
> 3) Add a device-tree.bbappend and add to the device-tree whatever value(s)
> you need. If you want to use the Linux kernel sources for your device-tree,
> you
> can "restore" the lines that were disabled in the devicetree class:
>
> ...
>
> KERNEL_INCLUDE ??= " \
> ${STAGING_KERNEL_DIR}/arch/${ARCH}/boot/dts \
> ${STAGING_KERNEL_DIR}/arch/${ARCH}/boot/dts/* \
> ${STAGING_KERNEL_DIR}/scripts/dtc/include-prefixes \
> "
>
> (the python block runs AFTER the variables are processed, so the bbappend
> approach works fine.)
Yep, this is exactly how I did it initially, but it felt dirty.
>
> But speaking more toward your specific example of the gpio stuff. There IS a
> copy of the gpio.h file inside of the device-tree repository. (More on that
> below)
>
> > I sort of get the impression that the DTS coming from
> > gen-machineconf/lopper are not intended to be hand edited? (they've
> > got phandles for some reason, which are just noise)
>
> The workflow we designed is:
>
> Vivado -> XSA
> XSA -> SDTGen -> SDT artifacts
> (SDT artifacts can modify them here)
> SDT artifacts -> gen-machine-conf -> YP config & domain DTS
> (YP config & domain DTS files can be modified here)
> YP build
>
> In the two places above where the artifacts can be modified, we highly
> recommend NOT modifying things by hand. Instead write a script to do it in a
> reproducible way. We expect that every time you regenerate your XSA you will
> need to go through the process, including SDTGen and gen-machine-conf, so
> being able to apply your customization in an automated approach really is what
> you want.
I think I see. For example, if I am adding an I2C GPIO expander (which needs
some defines from the #include), then I could write a script which adds it to
the bus and feed that to gen-machine-conf? Assuming that's right, are there any
examples of such scripts? I can't find any arguments (in
https://github.com/Xilinx/gen-machine-conf/blob/main/gen-machineconf) where I
might pass them.
Regarding scripting the XSA -> SDT step, I suppose that the purpose there is
for transformations/modifications that are applicable to all domains (e.g.
FSBL, not just Linux)?
> So if you need to customize (or synchronize?) the gpio.h with your
> development, I think it can be done early as a patch to the SDTGen device-tree
> repository that is being used, then everything "should" flow through the
> system
> automatically. (Note, I've never done this, but it's my understanding of how
> you can approach this.)
I won't need to modify gpio.h - rather, just utilize its #defines in my own
bindings.
> > A little guidance would be appreciated.
>
> Hopefully the above helps. I'm far from an expert on DTS files and how they
> should be done. I tried to influence the overall workflow in a way that both
> beginners and experts can find it useful. If you have suggestions, please
> let us
> know.
>
I think it helps a lot, so thanks again :)
>
> One final note, we're also aware of some situations where you may need
> multiple device-trees (at the same time) for different board revisions. At
> this
> point I don't have good suggestions how to manage this. Best I can suggest is
> run gen-machine-conf multiple times, manually copy out the device-trees you
> want and then create a custom device-tree recipe that builds and packages
> them all however you need them. (This is far from simply unfortunately.)
I'll need to do something like this internally soon - I'll let you know what I
decide on. To be honest, I might end up hijacking the device-tree recipe via
bbappend to apply some .dtsi overlays.
Thanks,
Chris
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