[PATCH] dt-bindings: exynos: Document #sound-dai-cells property of the HDMI node

[Marek Szyprowski]

Hi Inki,

On 2018-03-08 07:50, Inki Dae wrote:
> 2018년 03월 08일 15:29에 Marek Szyprowski 이(가) 쓴 글:
>> On 2018-03-08 05:01, Inki Dae wrote:
>>> 2018년 03월 08일 02:11에 Sylwester Nawrocki 이(가) 쓴 글:
>>>> The #sound-dai-cells DT property is required to describe link between
>>>> the HDMI IP block and the SoC's audio subsystem.
>>>>
>>>> Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com>
>>>> ---
>>>>    Documentation/devicetree/bindings/display/exynos/exynos_hdmi.txt | 3 +++
>>>>    1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/display/exynos/exynos_hdmi.txt b/Documentation/devicetree/bindings/display/exynos/exynos_hdmi.txt
>>>> index 8715ff06c457..6b2a526ec586 100644
>>>> --- a/Documentation/devicetree/bindings/display/exynos/exynos_hdmi.txt
>>>> +++ b/Documentation/devicetree/bindings/display/exynos/exynos_hdmi.txt
>>>> @@ -50,6 +50,9 @@ Required properties for Exynos 5433:
>>>>    - clock-names: aliases for above clock specfiers.
>>>>    - samsung,sysreg: handle to syscon used to control the system registers.
>>>>    +Optional properties for Exynos 4210, 4212, 5420 and 5433:
>>>> + - #sound-dai-cells: should be 0.
>>>> +
>>> Just trivial question. 'sound-dai-cells' property could affect hdmi driver? I looked into HDMI codec driver but I didn't find relevat code.
>>> I mean that if this property never affect HDMI driver then this property would be a dead thing even through this can be declared optionally.
>> This property is used by ASoC framework when it is building connections
>> between all elements of the virtual 'sound card'. It allows generic
>> code to find proper driver for the digital audio interface (DAI) object.
> I also assumed that some place of ASoC framework checks this property. For this I looked into HDMI codec driver(sound/soc/codecs/hdmi-codec.c) and relevant interfaces of ASoC framework.
> But I couldn't find it. :( Could you let me know which code of ASoC framework checks this? I saw this property only in 'snd_soc_of_get_dai_name' and 'snd_soc_of_get_dai_link_codecs' functions but seems these functions aren't called by the HDMI codec driver.

It is used by snd_soc_of_get_dai_link_codecs() function, which is called
from respective board/machine driver. See sound/soc/samsung/odroid.c for
good example. It allows to automatically create connection to max98090 and
hdmi codec devices, which are specified in 'sound/codec' node (see
exynos5422-odroidxu3-audio.dtsi).

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland