Re: devicetree repository separation/migration

[Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

On Tue, Feb 18, 2014 at 02:44:15PM -0800, Tim Bird wrote:
> I'm not in favor of separating the device tree information from the kernel.
> 
> If we switch, then whatever synchronization issues other projects
> are having now with synching with the device tree info from the kernel will
> just then become the problem of the kernel developers, who will then
> have to sync with the device tree info from another repository.  If the
> sync issues can't be solved now for them, why or how would it be solved
> post-separation for us?  (It sounds like a zero-sum game of pain transfer
> to me.)
> 
> I'm relatively unfamiliar with the arguments.  Can someone provide
> a brief list of reasons this is needed, and how the inconvenience to Linux
> kernel developers will be minimized, should it proceed?

One of the reasons for doing devicetrees is to separate the hardware
description from the code so that:
- Other OSes (and bootloaders) can use the same description to start on
  a given hardware
- A generic Kernel can be started on any hardware
- A hardware describes itself, makes itself more introspecitve so we can
  go away from very specialized kernels

This can't be archieved when the devicetrees are constantly changing. So
we should separate the devicetrees from the kernel to make them usable
for other projects, but also to make the kernel more universally usable.
Compatibility issues will be far more obvious when kernel and
devicetrees are separated, but this will make people behave more
carefully and helps making the devicetree interface more stable and
usable.

Just to make that sure: It's an illusion that future kernels will be
100% compatible with old devicetrees, but we should at least follow a
best effort approach. If they are compatible enough to at least bring up
the hardware then this is at least enough to install a better
devicetree.

Sascha

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