Re: [RFC PATCH 0/9] Thumb-2 ISA kernel port

[Ralf Baechle <ralf@linux-mips.org>]

On Wed, Jun 06, 2007 at 08:29:14PM +0200, Sam Ravnborg wrote:

> > Because of the issues listed below, merging the Thumb-2 support into
> > the existing arch/arm files would clutter the existing code with
> > macros like ARM, THUMB or W (for conditional compilation and the wide
> > instruction format). The IT instruction is also not recognised by
> > older toolchains and additional (assembler) macros would be needed,
> > including support for the inline assembly. I therefore decided to
> > create a separate arch/arm_t2 directory that shares a lot of code with
> > the existing arch/arm.
> 
> Hi Catalin.
> Can you please share with us the strong arguments why another (third)
> arm architecture are needed?

It's been my experience with 64-bit MIPS that starting off with a 2nd
arch then eventually factoring out the differences and unifying things
back into a single mips architecture was actually the easier road to go.

Downside: this approach takes long term careful coding.  It is hell with
the kind of "code once and resuse never" style that's only too common in
the embedded industry.

  Ralf