Hi all,
Apologies if this isn't the right forum (my thinking was, is that it is related to sound, and thus ALSA, more) - however, if it isn't, please let me know where I could forward this query (maybe devicetree mailing list ?)
I have tried, but I really cannot find any documentation where I can read about, what does conceptually #sound-dai-cells in a device tree mean.
Most I've found so far, is:
linux_git$ grep -r 'sound-dai-cells' --exclude-dir='.git' arch/arm/boot/dts/sun7i-a20-cubietruck.dts: #sound-dai-cells = <0>; ... arch/arm/boot/dts/r8a7790.dtsi: * #sound-dai-cells is required arch/arm/boot/dts/r8a7790.dtsi: * Single DAI : #sound-dai-cells = <0>; <&rcar_sound>; arch/arm/boot/dts/r8a7790.dtsi: * Multi DAI : #sound-dai-cells = <1>; <&rcar_sound N>; ... Documentation/devicetree/bindings/sound/hisilicon,hi6210-i2s.txt:- #sound-dai-cells: Should be set to 1 (for multi-dai) ...
As far as I can tell:
* if it is 1, then you can refer to "ports" (?) of a soundcard node, i.e. <&rcar_sound N>; * if it is 0, then you cannot refer to "ports", and you can only refer to <&rcar_sound>
Also, it seems to appear only in these kernel source files:
drivers/misc/atmel-ssc.c: if (!of_property_read_bool(np, "#sound-dai-cells")) drivers/misc/atmel-ssc.c: if (of_property_read_bool(ssc->pdev->dev.of_node, "#sound-dai-cells")) ... sound/soc/generic/simple-card.c:#define CELL "#sound-dai-cells" ... sound/soc/generic/simple-scu-card.c:#define CELL "#sound-dai-cells" ... sound/soc/soc-core.c: "#sound-dai-cells", 0, &args); sound/soc/soc-core.c: "#sound-dai-cells"); sound/soc/soc-core.c: "#sound-dai-cells",
... so, I guess, it only has meaning in what would be nodes under `target = <&sound>;` in a device tree - is that correct?
But then - what is sound-dai-cells actually describing? Number of entries in `static struct snd_soc_dai_driver` of a (codec?) driver, if it is defined as an array? Or a number of DAI links?
Could anyone offer a more proper conceptual description of what #sound-dai-cells is supposed to describe?
Many thanks in advance for any pointers, s.