[gentoo-dev] [RFC] subprofiles for ARM architecture

[Raúl Porcel]

Hi,

The other day Markus(maekke) found an issue i encountered two years ago.
An app supports only a subarchitecture of the ARM architecture.

For those that don't know the ARM architecture, its an architecture
which is mostly used on embedded and/or mobile devices(cell phones,
mostly), also there's now some stuff called smartbooks(Efika MX
smartbook, Asus Transformer, etc...) and smarttops(Efika MX smarttop).

The problem is that during the history of the ARM architecture(according
to the wikipedia, the architecture was introduced back in 1981) there
has been some subarchitectures(the most available are armv4, armv4t,
armv5t, armv6j and armv7-a) which include new functions that is not
available on the previous subarchitecture. Something like SSE, SSE2,
SSE3, etc... but in arm is called SIMD, NEON, etc...

Apart from that, there are some apps that only work in one
subarchitecture because it uses some capabilities only available on that
subarchitecture and newer. Which is the case of valgrind. It only works
with armv7-a. Also there's www-client/chromium, which later versions
only work on >=armv6j.

With subprofiles we could keyword such packages, mask them globally on
arm and unmask it on the subprofile of the subarchitecture that supports it.

We build stage3s for the armv4t, armv5te, armv6j, armv7a
subarchitectures, and we'll make them use the profiles.

Thanks