Re: devicetree repository separation/migration

On 2/19/2014 1:08 AM, Sascha Hauer wrote:

On Tue, Feb 18, 2014 at 02:44:15PM -0800, Tim Bird wrote:

quoted

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

Tim knows this ^^^^.  He was asking for the arguments for moving dts files
out of the linux kernel source tree.

Can you answer his question?

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.

So come up with a way of making dts files more stable while still in
the linux kernel source tree.  Moving the files to another repository
is not going to magically make them more stable.

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

-Frank
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