Re: [linux-sunxi] Re: [PATCH 11/11] arm64: dts: add Pine64 support
From: Danny Milosavljevic
Date: Tue Feb 09 2016 - 15:33:46 EST
Hi,
On Mon, 8 Feb 2016 11:55:43 +1100
Julian Calaby <julian.calaby@xxxxxxxxx> wrote:
> I believe that device tree overlays are the generally recommended method.
I agree. But last time I tried, the device tree compiler didn't
support overlays - neither in Debian nor in the in-kernel dtc ("-@" is
unsupported; last tried with linux-4.3-rc7).
And even if you could compile them, the platform has to support specifying which
overlays to use in the first place (for example as a Linux cmdline option).
For example Beaglebone Black (TI Sitara) does. I don't know whether sunxi does.
Also, the overlay dts files are very different from normal dts files, see
<http://www.patternagents.com/news/2015/01/29/devicetree-overlays.html>.
The original Linux device tree changeset patchset also introduced an in-kernel
interface for loading/unloading of DT overlays at runtime. AFAIK, this is still
not available to user space.
More info at <https://lwn.net/Articles/616859/>.
(I tried some 4 months ago - it wasn't integrated enough.
So now I just patch the main dts every time - which I probably shouldn't)
Regards,
Danny