Re: [PATCH 0/3] patches to allow DTB to be appended to the ARM zImage

On Jun 12, 2011, at 9:59 AM, Russell King - ARM Linux wrote:

On Sun, Jun 12, 2011 at 11:47:59AM -0400, Nicolas Pitre wrote:

quoted

On Sun, 12 Jun 2011, Russell King - ARM Linux wrote:

quoted

And we've ended up with a fucked up situation which is extremely
fragile, and actually makes me _NOT_ want to convert any existing
platforms to use DT in the least.

Agreed.  I don't think that anything older than OMAP2 is worth 
converting to DT.  The return on the investment is simply not worth it, 
other than for experimental purposes.

I think you haven't appreciated the situation - let's take PXA as an
example.  PXA has been around for years, and IP in the latest silicon
is present in many of the older silicons too.

There's two issues here:

1. If we port existing drivers over to use DT as a means to shrink the
size of the kernel, we need _all_ PXA using platforms to use DT.

2. If we continue having board support for PXA submitted, we want it to
use DT support.

The result will be a mess of some bits of PXA using DT, other bits using
statically declared stuff.  It may get to the point where on some PXA
platforms DT is used to describe some of the system, and on a different
PXA platform, it describes some other but needs some static stuff.

I don't see this as a sustainable way forward.  If we're going to move a
particular SoC over to DT, we need to move the entire SoC over.  We can't
do this half-heartedly.

And that means we _must_ deal with accepting ATAGs from existing boot
loaders, with that information taking precidence over the DT blob
supplied with the kernel.

The only other way out would be to have a small ATAG interpreter that modified/generated the DT so that the rest of the kernel could rely on it completely. This would fatten what is a very slim later right now, but it would mean the whole rest of the kernel could trust the DT blob as gospel.

Warner