linux-kernel - Re: [v5 PATCH 1/5] extcon: Add Type-C and DP support

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Date:	Thu, 14 Jul 2016 11:10:35 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Chris Zhong <zyw@...k-chips.com>, dianders@...omium.org,
	tfiga@...omium.org, heiko@...ech.de, yzq@...k-chips.com,
	groeck@...omium.org, myungjoo.ham@...sung.com, wulf@...k-chips.com,
	marcheu@...omium.org
Cc:	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [v5 PATCH 1/5] extcon: Add Type-C and DP support

Hi Chris,

On 2016년 07월 14일 11:07, Chris Zhong wrote:
> Hi Chanwoo Choi
> 
> On 07/14/2016 09:15 AM, Chanwoo Choi wrote:
>> Hi Chris,
>>
>> [snip]
>>
>>>>>> Thanks,
>>>>>> Chanwoo Choi
>>>>> There are 4 modes for Type-C DP alt mode:
>>>>> 1) USB host only  :
>>>>>
>>>>> extcon_set_cable_state(edev, EXTCON_USB_HOST, 1);
>>>>> extcon_set_cable_state(edev, EXTCON_USB, 0);
>>>>> extcon_set_cable_state(edev, EXTCON_DISP_DP, 0);
>>>>>
>>>>> 2) USB device only
>>>>>
>>>>> extcon_set_cable_state(edev, EXTCON_USB_HOST, 0);
>>>>> extcon_set_cable_state(edev, EXTCON_USB, 1);
>>>>> extcon_set_cable_state(edev, EXTCON_DISP_DP, 0);
>>>>>
>>>>> 3) DP only
>>>>>
>>>>> extcon_set_cable_state(edev, EXTCON_USB_HOST, 0);
>>>>> extcon_set_cable_state(edev, EXTCON_USB, 0);
>>>>> extcon_set_cable_state(edev, EXTCON_DISP_DP, 1);
>>>>>
>>>>> 4) USB + DP
>>>>>
>>>>> extcon_set_cable_state(edev, EXTCON_USB_HOST, 1);
>>>>> extcon_set_cable_state(edev, EXTCON_USB, 0);
>>>>> extcon_set_cable_state(edev, EXTCON_DISP_DP, 1);
>>>>>
>>>>>
>>>>> for 3rd mode: DP only, there is only EXTCON_DISP_DP is attached, the EXTCON_USB_HOST
>>>>> and EXTCON_USB are detached, Can I set the property into these 2 detached cable?
>>>>> or just call extcon_set_cable_state(edev, EXTCON_DISP_DP, EXTCON_PROP_TYPEC_POLARITY, 0 or 1);
>>>> I'm thinking to solve this issue. In result, we can add one more type to specific connector.
>>>> For EXTCON_DISP_DP, we can add the two type as following. And EXTCON_PROP_TYPEC_POLARITY property
>>>> should be added to EXTCON_TYPE_USB.
>>>>
>>>> +    [EXTCON_DISP_DP] = {
>>>> +        .type = EXTCON_TYPE_DISP | EXTCON_TYPE_USB,
>>>> +        .id = EXTCON_DISP_DP,
>>>> +        .name = "DP",
>>>> +    },
>>>>
>>>> So, as you mentioned, EXTCON_DISP_DP can set the EXTCON_PROP_TYPEC_POLARITY property as following:
>>>> - extcon_set_cable_state(edev, EXTCON_DISP_DP, EXTCON_PROP_TYPEC_POLARITY, 0 or 1);
>>>>
>>>> I'll again developing the extcon property.
>>>>
>>>> Thanks,
>>>> Chanwoo Choi
>>>>
>>> Nice idea, But I am thinking about is it compatible with real DisplayPort without Type-C.
>>> Maybe we should add a new cable: EXTCON_DISP_DP_ALT
>>>
>>> +    [EXTCON_DISP_DP] = {
>>> +        .type = EXTCON_TYPE_DISP,
>>> +        .id = EXTCON_DISP_DP,
>>> +        .name = "DP",
>>> +    },
>>>
>>> +    [EXTCON_DISP_DP_ALT] = {
>>> +        .type = EXTCON_TYPE_DISP | EXTCON_TYPE_USB,
>>> +        .id = EXTCON_DISP_DP,
>>> +        .name = "DP ALT",
>>> +    },
>> EXTCON_DISP_DP_ALT means EXTCON_DISP_DP connector with EXTCON_PROP_TYPEC_POLARITY property.
>> So, we can explain the DP alternative mode without EXTCON_DISP_DP_ALT.
>>
>> I'm wondering to add the new EXTCON_DISP_DP_ALT connector
>> because alternative mode was defined as mode instead of new h/w connector type.
>>
>> Thanks,
>> Chanwoo Choi
>>
>>
> Okay, so I think some comment for EXTCON_DISP_DP is necessary and enough.

Okay. I'll do that

Thanks,
Chanwoo Choi