ALSA: vsnd: Add Xen para-virtualized frontend driver

From: Oleksandr Andrushchenko <[email protected]>

This patch series adds support for Xen [1] para-virtualized sound frontend driver. It implements the protocol from include/xen/interface/io/sndif.h with the following limitations:
- mute/unmute is not supported
- get/set volume is not supported
Volume control is not supported for the reason that most of the use-cases (at the moment) are based on scenarious where unprivileged OS (e.g. Android, AGL etc) use software mixers.

Both capture and playback are supported.

Thank you,
Oleksandr

Resending because of rebase onto [2] + added missing patch

[1] https://xenproject.org/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/log/?h=for-next

Oleksandr Andrushchenko (12):
ALSA: vsnd: Introduce Xen para-virtualized sound frontend driver
ALSA: vsnd: Implement driver's probe/remove
ALSA: vsnd: Implement Xen bus state handling
ALSA: vsnd: Read sound driver configuration from Xen store
ALSA: vsnd: Implement Xen event channel handling
ALSA: vsnd: Implement handling of shared buffers
ALSA: vsnd: Introduce ALSA virtual sound driver
ALSA: vsnd: Initialize virtul sound card
ALSA: vsnd: Add timer for period interrupt emulation
ALSA: vsnd: Implement ALSA PCM operations
ALSA: vsnd: Implement communication with backend
ALSA: vsnd: Introduce Kconfig option to enable Xen PV sound

 sound/drivers/Kconfig     |   12 +
 sound/drivers/Makefile    |    2 +
 sound/drivers/xen-front.c | 2107 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 2121 insertions(+)
 create mode 100644 sound/drivers/xen-front.c

2.7.4