linux-kernel - RE: [PATCH v1 2/2] dt-bindings: extcon: Add Realtek DHC RTD SoC Type-C

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Date:   Thu, 24 Aug 2023 09:23:48 +0000
From:   Stanley Chang[昌育德] 
        <stanley_chang@...ltek.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
CC:     Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v1 2/2] dt-bindings: extcon: Add Realtek DHC RTD SoC Type-C

Hi Krzysztof,



> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Sent: Thursday, August 24, 2023 4:43 PM
> To: Stanley Chang[昌育德] <stanley_chang@...ltek.com>; MyungJoo Ham
> <myungjoo.ham@...sung.com>
> Cc: Chanwoo Choi <cw00.choi@...sung.com>; Rob Herring
> <robh+dt@...nel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>;
> linux-kernel@...r.kernel.org; devicetree@...r.kernel.org
> Subject: Re: [PATCH v1 2/2] dt-bindings: extcon: Add Realtek DHC RTD SoC
> Type-C
> 
> 
> External mail.
> 
> 
> 
> On 24/08/2023 09:23, Stanley Chang[昌育德] wrote:
> > Hi Krzysztof,
> >
> >>>>> +
> >>>>> +title: Realtek DHC RTD SoCs USB Type-C detection
> >>>>
> >>>> Type-c usually go to usb directory.
> >>>
> >>> This binding is not for a type-c controller.
> >>> It is an extcon device for type-c connector detection.
> >>> So I put it at extcon directory.
> >>
> >> If this is not a type-c controller, then what is it? Explain me
> >> please what is an "extcon device" without using any Linux subsystem
> naming.
> >
> > Sorry. "extcon device" may be the wrong name I'm using.
> >
> > As far as I know, type-c controller supports PD detection, role detection, role
> swap and cc configuration.
> > But in our SoC, type c module only supports role detection.
> > So I don't think it's a type-c controller.
> 
> So module handling some parts of "Type-C" is not a "Type-C controller"
> but if such module handles a bit more, it becomes Type-C?

Due to hardware function limitation, it can't handle the full function of type-c.

> >
> > I found a similar driver at
> > drivers/extcon/extcon-usbc-cros-ec.c
> > It belongs to External Connector, which can detect USB Type C cables.
> 
> That's a driver, not a binding...
> 
> >
> > So our driver is an external connector driver.
> 
> Driver yes, not binding.
> 
> >
> >>>
> >>> And I will add “connector” to the title.
> >>> title: Realtek DHC RTD SoCs USB Type-C Connector detection
> >>
> >> So usb...
> >
> > I refer to this binding, and it is in folder bindings/extcon.
> > docs/devicetree/bindings/extcon/extcon-usbc-cros-ec.yaml
> > Title: ChromeOS EC USB Type-C Cable and Accessory Detection
> 
> So maybe it should be moved as well?
> 
> extcon is a Linux framework. If you think extcon is a type of hardware, then
> please tell me what it is exactly. Please define it. And then I wonder why the
> name "extcon" is anyhow connected to Type-C USB.
> 

Well, from my point of view. extcon stands for External Connector.
HDMI connector, micro USB connector, type-c connector are all a kind of hardware, they are external connectors.
I think the Type-C connector is a kind of extcon.
Of course, I agree that Type-C is part of USB.

So this binding can be usb or extcon, I don't think it is strictly restricted.

Thanks,
Stanley