Re: device tree compiler with overlay support?

[Michal Suchanek <hramrach-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 7 May 2015 at 09:28, Pantelis Antoniou
<pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org> wrote:
> Hi Geert,
>
>> On May 7, 2015, at 10:17 , Geert Uytterhoeven <geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org> wrote:
>>
>> On Tue, May 5, 2015 at 6:51 PM, Michal Suchanek <hramrach-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>> On 5 May 2015 at 17:18, Michal Suchanek <hramrach-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>>> where is a device tree compiler that can compile an overlay?
>>>>
>>>> The compiler at git://git.kernel.org/pub/scm/utils/dtc/dtc.git shrieks
>>>> there is a syntax error as soon as the /plugin/ tag is present.
>>>
>>> ok, so I found a dtc patch here https://lkml.org/lkml/2013/1/4/295
>>>
>>> This does not apply cleanly to current DTC but the parts that fail are
>>> due to cosmetic changes in the code so I went ahead and applied it.
>>
>> Thanks for the link! That patch indeed requires some manual rework.
>>
>>> However, the created blob is not what the kernel can accept into
>>> of_overlay_create so what do I do with the blob to load it?
>>
>> Use "OF: DT-Overlay configfs interface" from Pantelis?
>>
>> That depends on "configfs: Implement binary attributes", also from Pantelis,
>> which requires reverting commit 28444a2bde8d1695i ("configfs_add_file:
>> fold into its sole caller").
>>
>> All of the above require manual fixups to apply.
>>
>> Still have to try the actual loading, new to the overlay game on mainline
>> kernels (I did use it on boneblack with its original kernel and its overlay
>> manager).
>>
>
> Posted the patches recently, but for your convenience here’s the git tree.
>
> https://github.com/pantoniou/dtc/tree/dt-overlays5
>
> FWIW, I’ll post the capemgr patch today too.

FWIW here is a separate branch with the dt overlay stuff I am running.

https://github.com/hramrach/linux-sunxi/commits/dt-overlay

You might want to look at the small fixes there.

It is worth noting that with your version of the patch adding -@ dtc
option the built board dtbs do not contain the symbols needed for
overlays unless overlays are enabled. So far dtbs were static wrt
build options AFAIK. That is they were either built or not but unless
the sources in question changed the dtbs would be the same.
Introducing this option dynamically based on CONFIG_OF_OVERLAY makes
dtbs content config dependent which does not seem like a very good
idea.

In fact I think -@ should be the default on compilers that support it
and might be optionally turned off.

Maybe some statistic of the size of the symbol table so generated and
relative size increase  for various boards might be nice thing to
have.

Thanks

Michal
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