[J-core] Is a small Linux distribution available for J2 on Numato Mimas?

[Rich Felker]

On Sun, Aug 07, 2016 at 03:16:45PM +0200, txt.file wrote:
> It's probably easier to get involved in debian instead of starting a
> complete new port on another distribution. At least debian already has
> an SH4 port and there is already the plan to support J-Core.
> Running Ubuntu on a 50 MHz single core cpu sounds awful to me.
> 
> Gentoo also has an SH4 port.

To be able to use Debian SH4 directly on J3/J4, several things would
have to happen:

- Either we'd need to add a little-endian build option for J-Core (I
  think this would be a good idea to work on soon if it's not too
  hard) or everything would have to be rebuilt for a big-endian
  variant.

- To support SMP, glibc would need to add runtime atomics selection
  with support for cas.l rather than hard-coding gusa, which is
  fundamentally UP-only. Having the kernel provide a vdso function for
  atomics might be a good idea since SH has so many variants.

Also, while Debian is a great resource in terms of its extensive
package coverage, it also tends to have very large install-size and
runtime memory needs, and so it may not be ideal for much of the early
hardware people will be using for J3/J4. It would be useful to get
J3/J4 support for lighter distributions too. I've looked into what
would be needed to boot an Alpine SH target and it doesn't look too
hard. I was pointed to the scripts that were used for bootstrapping
existing targets here:

http://dev.alpinelinux.org/~tteras/bootstrap/

Rich