[Buildroot] [PATCH v3 0/7] dtc: update and add raspberry pi overlay support

[Peter Seiderer]

Hello Yann,

> Gesendet: Sonntag, 18. Januar 2015 um 17:49 Uhr
> Von: "Yann E. MORIN" <yann.morin.1998 at free.fr>
> An: "Peter Seiderer" <ps.report at gmx.net>
> Cc: buildroot at busybox.net, "Fabio Porcedda" <fabio.porcedda at gmail.com>, "Jeremy Kerr" <jk at ozlabs.org>, "Thomas Petazzoni" <thomas.petazzoni at free-electrons.com>, "Matthew Weber" <matthew.weber at rockwellcollins.com>
> Betreff: Re: [PATCH v3 0/7] dtc: update and add raspberry pi overlay support
>
> Peter, All,
> 
> On 2015-01-13 20:40 +0100, Peter Seiderer spake thusly:
> > There are two different dtb files used for raspberry pi booting:
> > - overwrite the firmware provided videocore dtb configuration ([1])
> > - linux kernel dtb configuration and dtb overlays ([2])
> 
> Well, I haven't yet tried to use overlays, but from what I understood,
> DTB overlays can be handled seamlessly from the RPi bootloader:
> 
>     device_tree_overlay=path/to-overlay.dtb
> 

Yes thats the way you 'activate' a given overlay...

> So, is it really required that we do patch dtc for overlay support?
> 

Yes, you have to patch the dtc tool to be able to generate a suitable overlay dtb file...

> Instead, I would very much prefer we stick to what upstream dtc provide,
> and when overlay support has been merged in there, we can bump our dtc
> version (or backport just the overlay support if bumping is not
> practical).

This means no overlay dtb file generation until 'official' support (do not know if
the patches where ever suggested upstream)?

> 
> It would be very unmaintainable to bundle overlay support in Buildroot,
> if upstream eventually decide to not support them, or decide to support
> them in a very different way. We can not afford this, I'm afraid.
> 

If this happens the 'patch' support could be dropped easily...

> In the meantime, and that's unfortunate, we won't support overlays in
> dtc... :-(
>

Though people have to find the right patches again and again...

But I understand the point that patch care in buildroot is not easy...

Regards,
Peter

> Regards,
> Yann E. MORIN.
> 
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