On Mon, May 20, 2019 at 03:18:08PM -0600, Simon Glass wrote:
> Hi David,
>
> On Sat, 24 Nov 2018 at 02:52, David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, Nov 14, 2018 at 04:29:23PM -0800, Simon Glass wrote:
> > > Hi David,
> > >
> > > We had a discussion today about a possible new v18 DT format[1]
> > >
> > > You have seen Frank Rowand's design from January[2]. Frank presented
> > > material at the conference[3] and I wrote up something up too [4].
> >
> > Yes, I didn't like the original proposal very much - overly
> > complicated, but the revised one I suggested back looks reasonably
> > do-able.
>
> Did that move ahead? I have been a little submerged for a while.
If it has, I haven't heard about it.
> > Your proposal seems to have a rather different focus from Frank's -
> > his is mostly about cleaner handling of overlays and similar
> > extensions. Yours is mostly about size.
> >
> > Can I ask what's the concern here? I mean, first of all, I'm finding
> > it a bit hard to believe that a few kiB of device tree really mean
> > much in the context of a vaguely modern system. But more specifically
> > is the concern in-memory size? Or size on persistent storage, disk or
> > flash? Those two would be amenable to different approaches to
> > mitigate.
> >
> > > Obviously this is a big undertaking and there is no guarantee it will
> > > go anywhere, nor that everyone will agree.
> >
> > So, looking at your document, really the only approach that seems
> > likely to be worth the trouble from the numbers you present is (B).
> > Although for (B), I'm not quite sure how you're encoding things not to
> > disallow cases that we do actually want to support. (J) seems like it
> > might be an interesting approach, coupled with a variant of (B),
> > although the numbers you give aren't too promising.
>
> What do you think about adding type information to the .dtb format?
> That is in the 'detailed design' section.
By adding new tags we could add type information in a much less
intrusive manner than current proposals. That said, I'm pretty uneasy
about this. I'm concerned that if it's generally there, then
supposedly end-clients will start using it, fundamentally changing the
semantic model of the device tree[1]. DT type information should
really be something like ELF debug information - an aid to
intermediate tools, but not intended for use by the final consumer.
[1] You can make a case for changing the semantic model, but if you
want that you should really change the whole thing from the ground
up, not try to graft it onto the OF-style DT model.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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