On Mon, Aug 06, 2007 at 10:54:33PM +0200, Segher Boessenkool wrote:

quoted

Aha!  Ok, now I understand the sorts of situations you're talking
about.  By "not direct mapped", I thought you were talking about some
kind of access via address/data registers on some indirect bus
controller, rather than weird variations on endianness and
bit-swizzling.

Hrm.. this is a property of how the flash is wired onto the bus,
rather than of the flash chips themselves, so I'm not entirely sure
where description of it belongs.

Simplest option seems to me to add a property "endianness" or
"bit-swizzling" or something which can be defined to describe some odd
connections.  If absent we'd default to direct mapping.  Segher, is
that idea going to cause you to scream?

No, that's fine with me.  I would recommend either using a
_good_ _descriptive_ name for such a property describing the
swizzling, if this swizzling is common; or just put the whole
bloody weirdo address permutation into some nice big array,
something like

address-permutation = <0 1 3 2 4 5 7 6 e f d c a b 9 8>;

Yes, I was contemplating something like that.

[snip]

quoted

So I left out ranges, on the grounds that there isn't actually
anything at present which will attempt to access flash partitions
"generically" as a device tree device.

It looks good to me like this.

In a real OF, the "register" access for the flash partition
node would be handled by its parent node, which would know
to do the direct-mapping thing (at least mapping it to _its_
parent, which typically asks the nodes further up, etc.)

For the kernel world, we should just document it in the binding.

quoted

I'm not sold on this approach, but I haven't heard you give a better
argument yet.

I haven't heard or thought of anything better either.  Using "ranges"
is conceptually wrong, even ignoring the technical problems that come
with it.

Why is "ranges" conceptually wrong?

To be honest this looks rather to me like another case where having
overlapping 'reg' and 'ranges' would actually make sense.

-- 
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				| _way_ _around_!
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