[flashrom] [PATCH] Add support for SPARC (maybe).

Stefan Tauner stefan.tauner at alumni.tuwien.ac.at
Sun Feb 8 22:16:37 CET 2015


On Sun, 08 Feb 2015 17:55:10 +0100
Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> wrote:

> On 07.02.2015 19:49, Stefan Tauner wrote:
> > Was implemented by SPARC newbies, does (cross-)compile but is not run-tested.
> >
> > Signed-off-by: Stefan Tauner <stefan.tauner at alumni.tuwien.ac.at>
> 
> Thanks!
> 
> Quoting wikipedia:
> > The endianness of the 32-bit SPARC V8 architecture is purely
> > big-endian. The 64-bit SPARC V9 architecture uses big-endian
> > instructions, but can access data in either big-endian or
> > little-endian byte order, chosen either at the application instruction
> > (load/store) level or at the memory page level (via an MMU setting).
> > The latter is often used for accessing data from inherently
> > little-endian devices, such as those on PCI buses.
> 
> If that is true, we are totally screwed. How can we even begin to
> influence the instructions emitted by the compiler? And if the compiler
> emits bigendian instructions by default, can that be overridden via MMU
> setting? If yes, does Linux use the endianness manipulation via MMU for
> PCI devices, in which case we'd have to treat the architecture as
> littleendian from a flashrom POV?
> 
> This is a nightmare.
> 

Only if you make it one. :)
Maybe this allows you to sleep better:
https://gcc.gnu.org/ml/gcc-patches/2011-10/msg02240.html

I am not sure if that "MMU settings" in wikipedia is referring to the
address space identifiers (ASIs), but it definitely screams [citation
needed]. 
In general the whole thing looks like a rather exotic if not esoteric
feature added to make porting Windows easier... in any case I am very
confident that it will not be encountered on real machines/OSes.

So... the only question is if you agree and we commit this before
tagging 0.9.8-rc1 or not. I don't care too much about SPARC support,
but I *do* care about getting the release out. Please respond in a
timely manner.

-- 
Kind regards/Mit freundlichen Grüßen, Stefan Tauner




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