Re: [gentoo-dev] splitting out arm keywords

[Joshua Kinard <kumba@gentoo.org>]

On 07/08/2014 21:48, Matthew Thode wrote:
> arm has a historical problem with stabilization, while keywording
> doesn't require access to all arm sub-arches the problem with the
> stabilization slowness causes running a full ~arm to become hard.  By
> that I mean that if someone keywords something for arm because it works
> on armv7 and I run ~arm because stabilization takes forever then my
> system may break because of both non-stabilized packages and because I
> could be running armv6.
> 
> In any case I propose splitting out arm into armv4, armv5, armv6 and
> armv7.  armv8 seems to be here already as arm64.

Couldn't this be better handled with some profile work?  These sound like
versions of Instruction Set Architectures.  In the MIPS world, you have your
original ISAs, mips1 through mips4, then you have the newer variants of
mips32r* (branches from mips2) and mips64r* (branches from mips4).  Anything
supporting mips4 could also support earlier ISAs.  Throw in our three
supported ABIs (o32, n32, n64), and machine-specific curiosities (SGI,
Cobalt, Yeelong/Loongson, etc), and life can be quite fun.  But we can cover
all of this with just a single 'mips' keyword in the tree.

Is that similar to how these ARM variants work?  Can an armv7 run code for
armv6 and earlier?

Splitting 'arm' into four new keywords, on top of 'arm64' is just going to
give you guys major headaches later.  You might even consider dedicated USE
flags for the arm subvariants and use those to control things in an ebuild
where applicable.


> I think this would be beneficial because of not all developers that want
> to help with arm have or what all the sub-arches necessary.  It also
> allows us to move faster on stabilization because most of us have access
> to armv7 a bit easier.  This would take some pressure off of the people
> doing stabilization for older sub-arches, but not much.

What's the support status of Gentoo on the older variants, such as armv4 and
armv5 stuff?  How fast is the CPU clock on those?  Do they include L2/L3
cache?  Lots of memory?  Generally, anything that could be a bottleneck or
severely increase the build time should be weighed against the potential
number of users and possibly support dropped if there aren't enough
developers or contributing users to maintain it.

I.e., w/ MIPS, we don't support anything under the mips3 ISA, which includes
DECStations (Debian does support those).  Build times would just be
tremendously slow and I haven't seen a lot of desire to support those.

-- 
Joshua Kinard
Gentoo/MIPS
kumba@gentoo.org
4096R/D25D95E3 2011-03-28

"The past tempts us, the present confuses us, the future frightens us.  And
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