[Intel-gfx] [PATCH i-g-t v2 3/3] docs: Add user documentation about audio support

[Lyude Paul]

With some small typos I fixed (nothing major):

Reviewed-by: Lyude Paul <lyude at redhat.com>

I've already pushed the patches upstream, thanks!

On Mon, 2017-08-28 at 11:12 +0300, Paul Kocialkowski wrote:
> This introduces plain-text documentation about the audio test, aimed
> at
> users who wish to setup and run the audio tests.
> 
> Given the contents of this documentation, it felt more relevant to
> make
> it part of the tree instead of the API reference.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski at linux.intel.com>
> ---
>  docs/audio.txt | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
>  create mode 100644 docs/audio.txt
> 
> diff --git a/docs/audio.txt b/docs/audio.txt
> new file mode 100644
> index 00000000..158ad5d1
> --- /dev/null
> +++ b/docs/audio.txt
> @@ -0,0 +1,45 @@
> +Audio Support in IGT
> +====================
> +
> +This document provides information and instructions about audio
> support in IGT.
> +
> +Introduction
> +------------
> +
> +The audio test is aimed at testing the audio features of display
> connectors,
> +such as HDMI.
> +
> +Test setup
> +----------
> +
> +The setup required for the audio test consists of using an HDMI-VGA
> adapter with
> +an audio-out 3.5 mm jack to extract the audio from the HDMI
> interface.
> +The audio-out jack is connected back to the device-under-test's
> line-in.
> +
> +Depending on the behavior of the adapter, it may be necessary to
> connect a
> +ghost VGA dongle to it (in order to emulate a connected display) to
> enable the
> +audio output. There are guides available detailing how to build
> these.
> +
> +When executed, the test will automatically send the test audio
> signal to all
> +ALSA audio HDMI outputs and record from the standard ALSA capture
> device.
> +
> +Configuration
> +-------------
> +
> +In order to deploy the test, ALSA controls have to be configured to
> set the
> +ALSA capture source to line-in. On Intel x86 systems, this can be
> achieved
> +with the following calls to the amixer utility:
> +# amixer sset Line 31 on
> +# amixer sset "Input Source" Line
> +
> +It is then useful to store the ALSA state permanently with the
> alsactl utility:
> +# alsactl store
> +
> +These settings can be restored with the alsactl utility:
> +# alsactl restore
> +
> +It is desirable to ensure that the alsa-restore and alsa-state
> systemd services
> +are enabled to do this job automatically, especially in the case of
> an
> +automated testing system:
> +# systemctl enable alsa-restore
> +# systemctl enable alsa-state
-- 
Cheers,
	Lyude