bcm2708: alsa sound driver

Signed-off-by: popcornmix <popcornmix@gmail.com>

alsa: add mmap support and some cleanups to bcm2835 ALSA driver

snd-bcm2835: Add support for spdif/hdmi passthrough

This adds a dedicated subdevice which can be used for passthrough of non-audio
formats (ie encoded a52) through the hdmi audio link. In addition to this
driver extension an appropriate card config is required to make alsa-lib
support the AES parameters for this device.

snd-bcm2708: Add mutex, improve logging

Fix for ALSA driver crash

Avoids an issue when closing and opening vchiq where a message can arrive before service handle has been written

alsa: reduce severity of expected warning message

snd-bcm2708: Fix dmesg spam for non-error case

alsa: Ensure mutexes are released through error paths

alsa: Make interrupted close paths quieter

BCM270x: Add onboard sound device to Device Tree

Add Device Tree support to alsa driver.
Add device to Device Tree.
Don't add platform devices when booting in DT mode.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

bcm2835: access controls under the audio mutex

I don't think the ALSA framework provides any kind of automatic
synchronization within the control callbacks. We most likely need
to ensure this manually, so add locking around all access to shared
mutable data. In particular, bcm2835_audio_set_ctls() should
probably always be called under our own audio lock.

snd-bcm2835: Don't allow responses from VC to be interrupted by user signals

There should always be a response, and retry after a signal interruption is not handled, so don't report
we are interruptible.

See: https://github.com/raspberrypi/linux/issues/1560

snd-bcm2835: Use bcm2835_hw params in preallocate