Raspberry Pi interview: Eben Upton reveals all (Linux User) [LWN.net]

Raspberry Pi interview: Eben Upton reveals all (Linux User)

Posted Mar 6, 2012 12:02 UTC (Tue) by wookey (guest, #5501)
In reply to: Raspberry Pi interview: Eben Upton reveals all (Linux User) by jspaleta
Parent article: Raspberry Pi interview: Eben Upton reveals all (Linux User)

And the reality is in the long term the multiarch concept being pushed forward inside Debian and Ubuntu now should make the problems with having to expense and maintain dedicated native build infrastructure for each arch moot.

You appear to be thinking multiarch does more than it does. Multiarch lets you co-install multiple ABI libraries (and headers). It thus simplifies and regularises classical cross-compiling somewhat. It doesn't solve the problem that you can't run 'armhf/hardfp' binaries (which pass parameters in the VFP registers on a v7 ARM) on an earlier ARM arch device (like the v6 PI various v5 'plugs' and the v4t openmoko and FAS chips) that doesn't _have_ the VFP registers. In practice there are now two common standards for making ARM binaries (out of far too many possible ways). v5(or v4t)/softvp and v7/hardfp. Those two cover all the arm hardware still available/in use in the world. Most distros have a v7 'hardfp' port for the real world (all phones, tablets, and current hardware) and a v4t or v5 'softfp' port for 'old stuff'. Most distros also have an unofficial/less supported v5 port and Debian is sticking with v4t for now as there are still enough openmoko, (and a few other devices) around to make that a sensible cutoff, as we do our best to be 'universal'. Those two build flavours still need hardware to be built on and whilst it isn't hard to build v4t or v5 binaries (i.e not using v6 or v7 instructions) on v7 hardware, that ability is nothing to do with multiarch. Cross-building softfp ('armel') binaries on a hardfp ('armhf') system, would use multiarch, but I'm not aware of anyone trying to do this for distribution builds. It's a great way of adding a load of new build failures you could do without. Multiarch makes it possible to cross-build a distro, but due to the inability to run tests other than via emulation it's always going to be more fragile, so I'm not sure anyone is actually going to use it for this for real distros. Getting some real hardware and building natively is always going to be a better plan IHMO.

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Raspberry Pi interview: Eben Upton reveals all (Linux User)

Posted Mar 6, 2012 16:56 UTC (Tue) by jspaleta (subscriber, #50639) [Link] (1 responses)

I'll cycle back and look at the multiarch capabilities and discussion in more detail.

If you are correct, and I am wrong, then it'll be that much more difficult for the external Ubuntu community to spin up support for this specific arch based entirely on sweat equity without buy-in from Canonical to provider the additional infrastructure and tie it into launchpad. That would be very unfortunate. I'd rather wish you were wrong, but I guess I'm holding out too much hope for the new technical capabilities to work around the corporate/community conflict of interest dynamic.

-jef

Raspberry Pi interview: Eben Upton reveals all (Linux User)

Posted Mar 6, 2012 18:46 UTC (Tue) by wookey (guest, #5501) [Link]

hmm, apologies for the total formatting fail in my previous comment. (Dear Jon - please bring us an 'edit' button so our incompetence, and failure to use 'preview' properly, need not remain for all to see).

wrt to distro support I'd say why not just use Debian on your Pi? No particular reason to use Ubuntu in this case. There is already a Debian image and it will no doubt become a supported platform.