Re: [PATCH v7 2/3] ASoC: qcom: dt-bindings: Add sc7180 machine bindings

On Thu, Sep 10, 2020 at 1:49 AM Rob Herring [off-list ref] wrote:

On Wed, Sep 9, 2020 at 3:24 AM Cheng-yi Chiang [off-list ref] wrote:

quoted

On Wed, Sep 9, 2020 at 4:34 AM Rob Herring [off-list ref] wrote:

quoted

On Mon, Sep 07, 2020 at 06:00:38PM +0800, Cheng-Yi Chiang wrote:

quoted

Add devicetree bindings documentation file for sc7180 sound card.

Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
---
 .../bindings/sound/qcom,sc7180.yaml           | 143 ++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/sound/qcom,sc7180.yaml

diff --git a/Documentation/devicetree/bindings/sound/qcom,sc7180.yaml b/Documentation/devicetree/bindings/sound/qcom,sc7180.yaml
new file mode 100644
index 000000000000..ae809346ca80
--- /dev/null
+++ b/Documentation/devicetree/bindings/sound/qcom,sc7180.yaml

@@ -0,0 +1,143 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/qcom,sc7180.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm Technologies Inc. SC7180 ASoC sound card driver
+
+maintainers:
+  - Rohit kumar <rohitkr@codeaurora.org>
+  - Cheng-Yi Chiang <cychiang@chromium.org>
+
+description:
+  This binding describes the SC7180 sound card which uses LPASS for audio.
+
+properties:
+  compatible:
+    const: qcom,sc7180-sndcard
+
+  audio-routing:
+    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+    description:
+      A list of the connections between audio components. Each entry is a
+      pair of strings, the first being the connection's sink, the second
+      being the connection's source.
+
+  model:
+    $ref: /schemas/types.yaml#/definitions/string
+    description: User specified audio sound card name
+
+  headset-jack:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: phandle of the codec for headset detection
+
+  hdmi-jack:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: phandle of the codec for hdmi jack detection

You already have links to these devices. Why duplicate it here?

What if you had 2 headsets? This doesn't scale.

Hi Rob, thanks for reviewing.
There was some discussion in
https://patchwork.kernel.org/patch/11737905/#23571643 about how to
specify the dailink that has a headset jack.
I would like to pass the information of headset jack and hdmi jack to
the machine driver so the machine driver can call
snd_soc_component_set_jack to set jack when init the corresponding link.
Headset jack and hdmi jack will be treated differently for button and
event type.
Because of this, we can not just set a property "jack" in the link.

Don't design your binding around some driver architecture. Limitations
of ASoC are not reasons for your binding.

For DP and HDMI, we assume HPD is supported generally as that's a
standard function for HDMI/DP controllers. There's a 'no-hpd' property
for cases of broken HPD. That hardware description is part of the
device HPD is connected to which is the HDMI/DP controller/bridge or
the connector node in the case of a GPIO line. That doesn't belong in
the virtual sound card.

I would assume a codec to be similar. The codec node (the alc5682
node) should have any jack related properties (or possibly implicitly
support it by default).

Thanks for the explanation. Now I can follow your thoughts.
I see that the sound card driver should assume that there is jack/hpd
available on HDMI/codec unless it is specified in HDMI/codec node
(should not specified in sound card).

quoted

As for the 2 headsets case (I guess you mean hp jack and mic jack), on
this board we will not have this use case.
If someone really wants to build hp jack and mic jack on the board
based on this machine driver, we can add two more property hp-jack and
mic-jack to specify that,
as the machine driver will need to know the different jack types
anyway. What do you think ?

I was thinking more of a case of having 2 of the same thing. Perhaps 2
HDMI outputs. Or if you have DP instead of HDMI? Just going to add
'dp-jack'?

I agree that this may not scale. It will become an abuse of binding interface.
Sound card drivers should have more knowledge/control on this kind of
configuration.
I think this can be taken care of inside the sound card driver.
If a machine wants a different configuration, we can use compatible
strings to achieve that.
This will be more flexible than the limited binding interface.

Thanks for the discussion, I will remove headset-jack and hdmi-jack in v8.

Rob