Re: Moving forward with sh2/nommu

[Rich Felker <dalias@libc.org>]

On Tue, Jun 16, 2015 at 03:38:59PM +0900, Yoshinori Sato wrote:
> > > > Thank you. I'd really like to make progress at least on the matter of
> > > > determining if this is feasible. I now have a new musl/sh2 patch that
> > > > simply uses "trapa #31" unconditionally, and it's a lot
> > > > simpler/cleaner and working on my patched kernel. The big question is
> > > > just whether this is an unacceptable constraint on hardware.
> > > 
> > > SH2A reserved system for vector 31.
> > > But not assigned now.
> > > I think no problem.
> > 
> > Thank you for the feedback. This sounds promising.
> > 
> > We still need whoever ends up being the new kernel maintainer for SH
> > to be okay with adding trap 31 syscall support for sh2 and declaring
> > it supported/stable for sh3/4 too, but at least it looks like there
> > arent technical problems for doing this.
> 
> Yes.
> I think test necessary by SH2A, but there would be no problems.

Do you know anyone who could verify that vector 31 is unused? There's
nothing in the upstream Linux kernel attached to it, but I'm not clear
on whether somebody would have to make a new SH2A chip variant
(unlikely) to use it for hardware purposes, or whether it could come
into use as a result of how an existing SH2A chip is wired up to other
hardware on the board.

Rich