N900 v3.19-rc5 arm atags_to_fdt.c is broken

On Tue 2015-01-27 13:50:22, Nicolas Pitre wrote:

On Tue, 27 Jan 2015, Russell King - ARM Linux wrote:

quoted

On Tue, Jan 27, 2015 at 10:16:24AM -0500, Nicolas Pitre wrote:

quoted

On Tue, 27 Jan 2015, Pavel Machek wrote:

quoted

(Note, that in 3.19 dts for n900 got too big, so we are actually
triggering old bugs. That means that this is a regression fix, and
should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Irrespective of that patch, I commented on another thread (about adding
the serial number to DT):

| How about something a little more radical.
| 
| Rather than trying to squeeze various ATAGs into DT, why don't we add a
| standard ATAG to contain the DT and pass that through into the kernel.
| This is IMHO how we _should_ have done the ATAG compatibility from the
| start.
| 
| That means we could get rid of most of the libfdt in the decompressor,
| and instead resolve the differences in the kernel.

That would allow us to get rid of all the FDT compatibility code in the
decompressor, and when we encounter these special ATAGs, we can deal with
them in the kernel instead of having to mess around with the DT.  I'd
also assume (although I haven't checked) that it would be much easier to
add additional DT properties in the kernel environment, rather than in
the rather restrictive decompressor environment.

Well...

I was initially against any ATAG-to-DT compatibility at all.  IMHO the 
"right" solution is to update the bootloader.

However people complained that updating the bootloader wasn't possible. 
I therefore suggested they go with a shim layer I termed the "impedance 
matcher" acting like an intermediate boot stage converting their (often 
unofficial and out-of-tree) ATAGs into proper DT nodes.  Some people did 
exactly that and it works wonderfully for them. It also works 
wonderfully for kernel maintenance as the platform specific tweaks are 
kept out of the kernel tree.

Still, that wasn't good enough for some cases as the move to DT 
regressed some platforms that just used to work before.  Concatenating a 
DTB to zImage was tolerable but installing an additional shim layer was 
too much.  Hence the ATAG-to-DT compat code in the decompressor.  This 
was meant to smooth things around the transition to DT, etc.  After all, 
those devices with non-replaceable bootloaders where shim layers are not 
possible should get out of commission eventually?

N900 is still phone that is best-supported by the mainline,
AFAICT. Yes, it is rather sad, but it means that no, it is probably
not going out of commission anytime soon.

									Pavel
-- 
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