Re: [PATCH] libfdt: add address translation support

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Tue, Apr 15, 2014 at 10:57:16PM +0100, Grant Likely wrote:
> On Tue, Apr 1, 2014 at 5:57 PM, Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > From: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> >
> > Add FDT based address translation. Currently, only simple bus
> > translations are supported, but the framework allows adding other
> > buses like PCI. Adding this to libfdt allows the address
> > translation code to be shared amongst u-boot, Linux kernel and other
> > projects.
> >
> > This code is based on GPL only licensed code. It must first be
> > re-licensed for dual GPL/BSD to add to libfdt which requires approval
> > from the copyright holders.
> >
> > This code is copied from u-boot common/fdt_support.c. The portion used
> > here was originally added to u-boot by Kumar Gala in 2010 and Freescale
> > is the copyright holder. Later changes have also only been done by
> > Freescale authors. The u-boot code appears to have been copied from the
> > Linux kernel's address translation code in drivers/of/address.c which
> > has no copyright. This code was moved by Grant Likely in 2010 and
> > originated from arch/powerpc/kernel/prom_parse.c which was written by
> > Ben Herrenschmidt.
> 
> Okay, so this makes things a bit more complicated. You need to compose
> a list of every commit that has touched this file in *both* the u-boot
> and kernel trees, and identify all of the copyright holders based on
> who submitted the patches. Once you have that list, then you need to
> get an Ack from every single one of them. If anyone does not respond,
> or does not give agreement, then we need to look at their change and
> determine whether or not we consider it to be a significant enough
> change that it would warrant copyright protection.

Actually, don't bother.

I'm not all that impressed by this translation code - in particular
the per-bus-type hooks don't make sense to me.  AFAIK the
interpretation of ranges is not bus specific. I think it will also
fail in some cases with #address-cells > 2, which is unfortunate.

I'm about to post my own implementation of address translation.

-- 
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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