This is a full-duplex audio driver for the ITE IT8172G Super RISC
companion chip, which contains, among many other peripherals,
an AC'97 digital audio controller.

This driver was based on the ES1371 audio driver, so it
shares some of the same characteristics of that driver.

ALaw/uLaw sample formats
------------------------

Like the ES1371 driver, this driver does not support the
ALaw/uLaw sample formats. See Documentation/sound/es1371.

Blocking vs. nonblocking IO
---------------------------

Like the ES1371 driver, this driver honours the O_NONBLOCK file
flag during open, read and write. See Documentation/sound/es1371.

Options
--------

This driver supports S/PDIF output and playback/record from
an I2S bus. These features are enabled/configured with the
following boot option format:

it8172=[spdif],[i2s:<I2S format>]

S/PDIF Support
--------------

The "spdif" option enables S/PDIF output. When enabled,
the analog AC'97 master and PCM channel outputs are muted,
and the SOUND_MIXER_WRITE_PCM ioctl can be used to set
the digital S/PDIF output volume.

I2S Support
-----------

The IT8172G audio controller can be configured to understand
three different data formats on the I2S bus. This is selectable
with the "i2s:<format>" option, where <format> is one of the
following:

dac: DAC, digital format
adc: ADC, DSP serial port
i2s: I2S mode

If the "i2s:<format>" is not given, "i2s:i2s" is assumed.

The driver accepts I2S ioctl's on the SOUND_MIXER_DIGITAL1
channel. So the I2S channel volume is settable with the
MIXER_WRITE(SOUND_MIXER_DIGITAL1) ioctl, and recording from
the I2S bus is accomplished by specifying SOUND_MASK_DIGITAL1
to the SOUND_MIXER_WRITE_RECSRC ioctl.


Steve Longerbeam
stevel@mvista.com
