About Beaglebone Black device tree

[Christian Mauderer]

On 31/01/2020 17:25, Christian Mauderer wrote:
> On 31/01/2020 16:04, Vijay Kumar Banerjee wrote:
>> Hi,
>>
>> While trying to run an rtems-littlevgl app on BBB, I found that the device
>> tree generated from the freebsd source matching the freebsd-org
>> HEAD commit doesn't work with the app and framebuffer device fails
>> to open. This is most likely due to the changes in the freebsd dts
>> sources because of which the overlay isn't working as expected.
> 
> If I remember correctly, SD card doesn't work either with a FDT that is
> too new.
> 
>>
>> I haven't had a detailed look at what's missing and the u-boot isn't
>> reporting any error in applying the overlay either. I checked that the
>> device tree built from freebsd tree matching the following commit
>> works:
>> 19a6ceb89dbacf74697d493e48c388767126d418
> 
> At the moment that's the right one. But that can change if someone
> updates libbsd again.

And I have to correct myself: That is not the right one. The current
libbsd HEAD should work with 6b0307a0a5184339393f555d5d424190d8a8277a.

> 
>>
>> This brings up two questions:
>> 1. Should we add the commit hash in the user manual so that the user can
>> build
>>     from source matching that commits instead of HEAD. This can be a
>> problem 
>>     as other codes ported from freebsd might break if the device tree
>> doesn't
>>     match the HEAD commit of freebsd-org
> 
> Adding a fixed commit id isn't really a good idea either. It is nearly
> guaranteed that no one updates it if libbsd is updated. It would be
> better to add instructions how to find out which commit should be used.

The command would be:

    git ls-files -s freebsd-org

It works regardless whether the sub-module is initialized or not.

> 
>>
>> 2. How do we manage the device tree overlays required by RTEMS or libbsd?
>>     I guess only BBB uses an overlay currently. Can we add a BSD license to
>>     the overlay and add it somewhere in rtems or rtems-libbsd repository and
>>     maintain it?
> 
> I think you wrote the overlay so you can add any license you want. But
> I'm really not sure where to put it. We currently don't have a location
> for that. Do you have a good suggestion?
> 
> Best regards
> 
> Christian
> 
>>
>> Best regards,
>> Vijay>
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