[U-Boot] [PATCH] disk:efi: avoid unaligned access on efi partition

[Piotr Wilczek]

Dear Albert and Måns,

> -----Original Message-----
> From: Måns Rullgård [mailto:mans at mansr.com]
> Sent: Monday, October 14, 2013 3:05 PM
> To: Albert ARIBAUD
> Cc: Piotr Wilczek; 'Tom Rini'; u-boot at lists.denx.de; 'Kyungmin Park'
> Subject: Re: [U-Boot] [PATCH] disk:efi: avoid unaligned access on efi
> partition
> 
> Albert ARIBAUD <albert.u.boot at aribaud.net> writes:
> 
> >> > Please do not advise using native unaligned accesses on code that
> >> > is not strictly used by ARMv6+ architectures: the present code,
> for
> >> > instance, might be run on pre-ARMv6 or non-ARM platforms, and
> thus,
> >> > should never assume ability to perform unaligned accesses
> natively.
> >>
> >> I'm advising no such thing.  I said two things:
> >>
> >> 1.  Declaring a struct with the 'packed' attribute makes gcc
> >>     automatically generate correct code for all targets.  _IF_ the
> >>     selected target supports unaligned ldr/str, these might get
> used.
> >>
> >> 2.  If your target is ARMv6 or later _AND_ you enable strict
> alignment
> >>     checking in the system control register, you _MUST_ build with
> the
> >>     -mno-unaligned-access flag.
> >
> > Then I apologize; I had read "Note that on ARMv6 and later ldr/str
> > support unaligned addresses unless this is explicitly disabled in the
> > system control register" as a suggestion to use that capability.
> 
> If building for ARMv6 or later, I do suggest allowing unaligned
> accesses.  The moment you add -march=armv6 (or equivalent), you allow
> for a number of things not supported by older versions, so why not
> unaligned memory accesses?
> 

Thank you for your comments, I will follow your advice.

Best regards
Piotr Wilczek

> --
> Måns Rullgård
> mans at mansr.com