linux-kernel - Re: [PATCH 1/2] dt-bindings: input: document Novatek NVT touchscreen controller

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Date: Thu, 23 May 2024 08:18:06 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Joel Selvaraj <joelselvaraj.oss@...il.com>,
 Hans de Goede <hdegoede@...hat.com>,
 Dmitry Torokhov <dmitry.torokhov@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-input@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: input: document Novatek NVT touchscreen
 controller

On 22/05/2024 16:00, Joel Selvaraj wrote:
> Hi Krzysztof Kozlowski,
> 
> On 5/21/24 11:48, Krzysztof Kozlowski wrote:
>> On 21/05/2024 14:09, Joel Selvaraj via B4 Relay wrote:
>>> From: Joel Selvaraj <joelselvaraj.oss@...il.com>
>>>
>>> Document the Novatek NVT touchscreen driver which is used in devices like
>>
>> driver? or device?
> 
> touchscreen "controller" would be correct I think. I will fix it in v2.
> 
>>> the Xiaomi Poco F1 [1]. Also, include the devictree binding file in the
>>> MAINTAINERS file.
>>>
>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts?h=v6.9
>>>
>>> Signed-off-by: Joel Selvaraj <joelselvaraj.oss@...il.com>
>>> ---
>>>   .../bindings/input/touchscreen/novatek,nvt-ts.yaml | 62 ++++++++++++++++++++++
>>>   MAINTAINERS                                        |  1 +
>>>   2 files changed, 63 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/novatek,nvt-ts.yaml b/Documentation/devicetree/bindings/input/touchscreen/novatek,nvt-ts.yaml
>>> new file mode 100644
>>> index 0000000000000..7839c6a028e4a
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/input/touchscreen/novatek,nvt-ts.yaml
>>> @@ -0,0 +1,62 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/input/touchscreen/novatek,nvt-ts.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Novatek NVT Touchscreen Controller
>>> +
>>> +maintainers:
>>> +  - Hans de Goede <hdegoede@...hat.com>
>>> +
>>> +allOf:
>>> +  - $ref: touchscreen.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - novatek,nvt-ts
>>
>> That's too generic. Looking at your driver change, it is not even needed.
>>
>>> +      - novatek,nt36672a-ts
>>
>> Eh, we have already panel. Why there is a need for touchscreen binding
>> (binding, not driver)?
> 
> I am not sure I understand this correctly. Help me a bit here. For 
> context, in mainline there is an existing driver for the novatek nvt 
> touchscreen controller. The driver did not have devicetree support. It 
> only had a i2c_device_id "NVT-ts". I don't know what is the variant of 

I just got a bit confused that you add another binding for the same
device, but now I see these are different interfaces - DSI and I2C.

> that Novatek touchscreen controller. To use the driver in Xiaomi Poco 
> F1, I introduced a devicetree compatible for it "novatek,nvt-ts". The 
> However, the Novatek touchscreen controller present in Xiaomi Poco F1 is 
> "NT36672A" which has a different chip id than the one in existing 
> driver. So I created a separate compatible for this touchscreen 
> controller variant "novatek,nt36672a-ts". I used compatible data to 
> differentiate the two variants. Since there are two variants, I am 
> mentioning both here.

Just to be clear, I don't care about driver here but hardware. You have
two separate interfaces on this hardware - DSI virtual channel and I2C?


Best regards,
Krzysztof