Bug#738760: libav: Add proper raspberry pi CPU detection

[Sebastian Ramacher]

Control: tags -1 + patch

Hi Peter

On 2015-01-03 22:36:13, peter green wrote:
> Sebastian Ramacher wrote:
> >there was a request to change the handling of the Raspberry Pi in the
> >libav package. Could you please explain the changes applied to the
> >Raspbian version?
> In raspbian we have a checker that runs after all our autobuilds (and I
> manually run a similar check when I do manual builds) that looks for files
> tagged as armv7 (note: it seems using neon compiler options causes files to
> be tagged as armv7 even if the CPU options aren't changed) and prevents the
> autobuilder from uploading them.
> 
> In general i've been adopting the principle that having armv7 code in
> raspbian is at best a pointless waste of space (if the code in question is
> correctly guarded behind runtime CPU detection) and at worst a serious
> problem (if it isn't). Therefore I have been responding to cases like this
> by simply disabling the armv7/neon code. The raspbian libav package got this
> treatment.
> 
> It's possible that I dodn't selct the best combination of flags, I'm no
> libav expert.
> 
> I have not tested whether an unodified debian libav package built in a
> raspbian chroot actually works on the Pi or not.

Thank you for the explanation. What about the attached patch? [1]

I've looked through the code and the only place where --enable-runtime-cpudetect
makes a difference is on powerpc (libavutil/ppc/cpu.c). Special handling for
Raspbian should not make a difference. Reinhard, is my reading of the code
correct?

Cheers

[1] Is this the right vendor in dpkg-vendor's terms?
-- 
Sebastian Ramacher
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