FCP-100: armv7 plan

[Russell Haley]

On Fri, Sep 8, 2017 at 4:11 PM, Warner Losh <imp at bsdimp.com> wrote:
> Greetings,
>
> This will serve as 'Last Call' for any objections to the plan to create an
> armv7 MACHINE_ARCH in FreeBSD, as documented in FCP-0100.
>
> Please see https://github.com/freebsd/fcp/blob/master/fcp-0100.md for all
> the details. This has been discussed in the mailing lists, on IRC, etc and
> I believe that I've captured the consensus from those discussions.
>
> I'm interested in any last minute comments, but as far as I can tell I have
> consensus on this issue. Absent any comments to the contrary, I'll proceed
> to having core@ vote that this document represents consensus. Now is the
> time to speak up if I've gotten anything wrong.
>
> Once the core vote is done, I plan on committing the code reviews I have
> open on this:
> https://reviews.freebsd.org/D12027
> and
> https://reviews.freebsd.org/D12010
> (again, I welcome any commits / criticisms in phabricator on the specific
> issues in this code)
>
> Thanks for any comments...
>
> Warner
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Hi Warner,

Thanks for your work on this. General thoughts in and around this subject.

1) I like how you split the commit into generic build system changes
vs BSP changes. It was helpful in aiding visibility in the code
changes.

2) Are these statements true?

- We will not be differentiating hard/soft float. It is assumed
armv6/7 are hard float (no letter suffixes)
- armv4/5 has no changes
- armv6 is split into armv6, armv7
- armv8 is aarch64
- We will not be supporting aarch64 32 bit extensions for running
armv6/7 binaries
- There is no way to run aarch64 on armv7

3) Can I ask if there will be other armv[0-9+]  architectures created
or do you think everything new will transition to 64 bit? If so, will
we (FreeBSD) be able to differentiate those architectures in the
future (aarch64v2)? I guess what I'm asking is "in your expert
opinion, have we taken enough steps to ensure clean
code/names/you-get-my-point for future changes?" What else could we
do? It seems that there is a lot of changes in arm compared to other
architectures. The rapid development of different things by the Arm
group and other vendors seems to cause a lot of churn. Do you think
our naming conventions do enough to take this into consideration?
Modern hardware manufacturing seem much different then what I am
reading about in Unix history. Have our naming patterns kept up?

4) Also, if my supposition about arm 32/64 compatibility is correct,
do we have plans in place for future boards may have 32/64 bit
compatibility like the RPi3? Or, is it just two different builds and
downloads? (which I'm cool with, but would like to know)

Cheers,

Russ