From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Lepore <ian-h+KGxgPPiopAfugRpC6u6w@public.gmane.org>
Subject: Re: [PATCH] libfdt: Remove special handling for unaligned reads
Date: Tue, 28 Jan 2020 19:15:03 -0700
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To: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Tom Rini <trini-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
Cc: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>, Devicetree Compiler <devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Patrice CHOTARD <patrice.chotard-qxv4g6HH51o@public.gmane.org>, Patrick DELAUNAY <patrick.delaunay-qxv4g6HH51o@public.gmane.org>

On Tue, 2020-01-28 at 08:08 -0600, Rob Herring wrote:
> On Tue, Jan 28, 2020 at 7:43 AM Tom Rini <trini-OWPKS81ov/FWk0Htik3J/w@public.gmane.org> wrote:
> > 
> > 
[...]
> > I still believe you have things wrong.  There's not an unaligned access
> > problem that libfdt needs to care about.  ARM doesn't need help handling
> > unaligned accesses.  The only problem that's been reported is from when
> > a user got themselves so far off in the weeds that nothing else matters.
> 
> I think while the vast majority of DTBs don't have anything that would
> cause unaligned accesses, that's not guaranteed by the FDT format.
> libfdt needs to handle the worst case.
> 
> What about ARMv5 and v4 which don't universally support unaligned
> accesses or any other architecture. Do all mips, openrisc, riscv, arc,
> microblaze, xtenza, etc. support unaligned accesses?
> 

Unaligned support is optional even on armv6 and armv7.  For quite a
long time freebsd ran armv7 chips with strict alignment (mostly because
we had no real need to do otherwise until people started complaining
that 3rd-party opensource software often failed on freebsd because it's
written with the assumption that the whole world is linux, and linux
used relaxed alignment).

-- Ian