Followup on ARM Minisummit at 2011 LPC

[David Rusling]

Jon,
	tardy but good.   I'm interested in LSB; just not sure what effort this
is...

Dave

On 26/09/11 14:37, Jon Masters wrote:
> [ Please forward this to anyone else who should get a copy - and ask
> them to signup to cross-distro at linaro because that's where we'll talk ]
> 
> Folks,
> 
> At the 2011 Linux Plumbers Conference in Santa Rosa, we held an ARM
> minisummit to discuss a few cross-distribution issues surrounding the
> "hard float" ABI for v7, and the ARM device and OS ecosystem in general.
> This mail is intended to summarize the key actions from that meeting.
> 
> 1). We discussed some of the different distributions (Debian, ChromeOS,
> Fedora, MeeGo, Mozilla, Ubuntu, etc.). We all agree on a common notion
> of what "hard float" means: it's the ARM AAPCS hardware floating point
> stuff in section 6, with the -d16 register set of the VFPv3 being used.
> Although there is some possibility to standardize v6, we decided we are
> interested only in the present and future at this point (and that's v7).
> 
> Some use Thumb2, some don't, but interworking allows for that (we in
> Fedora accidentally built a few packages with Thumb2 and will be undoing
> that without users even noticing). NEON is similarly an optional feature
> (supported by hwcaps) and not a required part of the core ABI. So it's
> really just the ABI that we all care about, and we all agree on it.
> 
> For toolchain folks, this means we all agree on the following:
> 
> --with-float=hard --with-fpu=vfpv3-d16 --with-abi=aapcs-linux
> 
> (some of us may target different optimizations, etc. of course but that
> is down to an application to decide whether it cares only about Cortex+)
> 
> 2). We agreed on the importance of cross-distro binary compatibility. It
> seems a number of distributions are excited by Debian's multi-arch
> approach (as am I), but not all of us will be moving to it any time
> soon. In the shorter term, if the runtime linker will have a special
> path, we can work around that with symlinks, but it's a kludge. Our
> preferred goal (from the meeting) is that everyone use this target:
> 
> arm-linux-gnueabihf
> 
> (Red Hat toolchains will include the vendor, but it is dropped by
> autotools when actually generating the paths and comparisons). I will
> advocate for Fedora ARM to switch to this target when possible, and in
> the interim will try to ensure we can establish some symlinks for the
> ability to run binaries compiled against Debian and Ubuntu on Fedora. I
> don't know what our timeline will be for this, but it's not something
> that's really landed everywhere yet. We at least agree on paths now!
> 
> 3). We agree that it is a good idea to do LSB. Adam Conrad (Canonical)
> and I agreed to represent community interests in driving this. We do
> know that we'll be preferring OpenGL ES 2.0 over OpenGL (same namespace
> within the library means one default choice is required). There will be
> many other things :) We agree that the main benefit to pursuing LSB is
> that it promotes the idea of working together and being compatible. It
> may be that we don't have the same level of compliance on ARM, but some
> level of conformance to some common standard(s) is a good start! :)
> 
> 4). We decided that we should have a standing Cross Distro meeting at
> Linaro Connect events, beginning with the next one in November. We will
> also facilitate a "show and tell" for apps at Connect, and have an
> opportunity to demo different distributions. We will add a specific
> session at the next Connect to continue this discussion.
> 
> Finally, we agreed we should keep the conversation going. I apologize
> for being a little tardy in sending this mail, but I want to kickstart
> further discussion and get this ball rolling again. I'll ping Adam about
> LSB (and thanks again to Jesse for the deep dive on GL). Meanwhile,
> David can grab ownership of organizing the Cross Distro meeting at
> Connect (I would like to assist). Anyone else got actions?
> 
> Jon.
> 
> 


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David Rusling, CTO

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