Add DAC driver support for Vybrid SoC

Hello,

This patchset adds support for the DAC peripheral on Vybrid SoC. Patchset is based on top of shawn's for-next branch and has been tested on a Toradex Colibri VF50 module.

@Jonathan
I kept the IIO_SHARED_BY_DIR instead of using IIO_SHARED_BY_ALL since this gives "out_conversion_mode" allowing me to distinguish this in the ABI documentation, that this is explicitly for the DAC.

Since 4.5-rc4 was released recently and assuming this makes it with this or next version, I assumed the target kernel version would be 4.6 and used that in ABI documentation.

Feedbacks and comments most welcome.

Changes since v2:
1. Add dependencies on OF and HAS_IOMEM in Kconfig
2. Fix ordering of disabling DAC and calling iio unregister

Changes since v1:
1. Fix return type of vf610_dac_init function
2. Document conversion modes in sysfs-bus-iio-vf610
3. Remove "indexed" specification from iio_chan_spec
4. Use "return" directly from default case in switch
5. Remove DRIVER_NAME
6. Call vf610_dac_init before iio device registration
7. Define and use vf610_dac_exit function in remove and suspend

v2 of the patchset
http://www.spinics.net/lists/arm-kernel/msg482839.html

v1 of the patchset:
http://www.spinics.net/lists/arm-kernel/msg481190.html

Thanks & Regards,
Sanchayan Maity.

Sanchayan Maity (2):
ARM: dts: vfxxx: Add DAC node for Vybrid SoC
iio: dac: vf610_dac: Add IIO DAC driver for Vybrid SoC

 Documentation/ABI/testing/sysfs-bus-iio-vf610      |   9 +
 .../devicetree/bindings/iio/dac/vf610-dac.txt      |  20 ++
 arch/arm/boot/dts/vfxxx.dtsi                       |  18 ++
 drivers/iio/dac/Kconfig                            |  10 +
 drivers/iio/dac/Makefile                           |   1 +
 drivers/iio/dac/vf610_dac.c                        | 298 +++++++++++++++++++++
 6 files changed, 356 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/vf610-dac.txt
 create mode 100644 drivers/iio/dac/vf610_dac.c

2.7.1