Re: OABI [was Re: COMPAT_NETBSD32 in GENERIC.common]

[Greg Troxel <gdt%lexort.com@localhost>]

Nick Hudson <nick.hudson%gmx.co.uk@localhost> writes:

> On 21/11/2018 07:32, Ryo Shimizu wrote:
>>
>>>> There are likely to be things that don't work yet on aarch64, I would
>>>> leave the kernel option on for now.
>>>>
>>>> MKCOMPAT=yes for aarch64 builds aarch64, earm and oarm though, I don't
>>>> think we need all of them.
>>>
>>> It does work already. That is the option.
>>
>> Currently COMPAT_NETBSD32 supports EABI only, and I will not be
>> supporting OABI in the future. There is also a technical reason
>> that sys/compat/netbsd32 can only have one instance.
>> #If someone is going to do it will support :)
>>
>> I think there is no need to build at least oarm with MKCOMPAT=yes.
>>
>
> It's time to retire support for oabi, imo.

I have been trying to understand exactly what is oabi vs eabi.   As
usual I will spiff up the wiki as people explain things to me.

Having read this:

  https://wiki.debian.org/ArmEabiPort

it seems oabi is only sensible for a small number of older ARM
processors with a kind of floating point unit that is not found on
anything recent.  Is that right?

So it would seem to me that there is essentially no reason for anyone to
run it, other than perhaps retrocomputing, and I have the impression
that even when retrocomputing, one can run eabi and it's better.

So "retire support for oabi" I would think means no longer allowing
"arm" and "armeb" MACHINE_ARCH variants in build.sh, no longer building
any oarm compat code, and dropping any local patches to gcc/clang that
add back oarm support that upstream doesn't have.  Or am I off?

Finally, I see some MACHINE_ARCH values in build.sh that I can't quite
map to the language others use.

earm means what processor architecture?  armv1 v2? v3?
earmhf means what particular kind of floating point unit?

earmv4: does that mean "armv4t", with thumb, which as I understand it is
pretty much every armv4 cpu except strongarm, wich is armv4 without
thumb?