Zero copy, and buildme change for Pi2

[6by9]

As per commit text.

• buildme dropped into the cross compile path when building on Pi2, so didn't install.
• enable zero copy within MMAL.

[6by9]

Ping @JamesH too.

[lurch]

I suspect you meant to ping @JamesH65 ? ;)

[popcornmix]

Does ENABLE_MMAL_VCSM default to:
mmal_port_parameter_set_boolean(m_vout_input, MMAL_PARAMETER_ZERO_COPY, MMAL_TRUE)

will that cause any issues?
What happens when "/dev/vcsm" is not accessible by non-root user? Does it fall back to non zero copy, or fail?

[6by9]

Default for MMAL_PARAMETER_ZERO_COPY is MMAL_FALSE, so this is only adding the capability for zero copy, not enabling by default.

Zero copy for MMAL_ENCODING_OPAQUE is done via a MMAL call for some reason, hence I suspect how you managed to get it working.
Zero copy for any other encoding will use /dev/vcsm, and will fail at the point the pool is created if that device is not accessible (hence our recent email thread over permissions on /dev/vcsm).

Oops over incorrect ping - thanks for amending.

[popcornmix]

Okay, so this PR shouldn't break anything (even if vcsm is not accessible)?
It will only potentially break when/if MMAL_PARAMETER_ZERO_COPY is requested in future?

[JamesH65]

Is vcsm now regarded as 'ok'? rather than experimental? (Not that I have any issues with this since by default it is off)

[6by9]

@popcornmix Correct - no changes by default with this PR. (Stuff I'm working on will benefit from zero copy, so I was enabling it from the start).

@JamesH65 vcsm seems to work on Pi fairly happily. Whether we consider it mainstream, or just an extra feature that may be of use is open to debate. I guess @pelwell would be the one to veto this if necessary, as any support burden is likely to fall at his door.