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Date: Tue, 07 Jun 2016 10:52:52 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Rob Herring <robh@...nel.org>
Cc: Venkat Reddy Talla <vreddytalla@...dia.com>,
MyungJoo Ham <myungjoo.ham@...sung.com>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Kumar Gala <galak@...eaurora.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [PATCH v4] extcon: gpio: Add the support for Device tree bindings
Ping.
Hi Rob,
I add some comment about gpio-keys and extcon-gpio.
I'm waiting for your reply.
On 2016년 05월 31일 23:34, Chanwoo Choi wrote:
> Hi Rob,
>
> On Tue, May 31, 2016 at 10:35 PM, Rob Herring <robh@...nel.org> wrote:
>> On Tue, May 31, 2016 at 2:35 AM, Chanwoo Choi <cw00.choi@...sung.com> wrote:
>>> Hi Rob,
>>>
>>> On 2016년 05월 31일 15:44, Chanwoo Choi wrote:
>>>> On 2016년 05월 28일 00:29, Rob Herring wrote:
>>>>> On Thu, May 26, 2016 at 05:17:45PM +0530, Venkat Reddy Talla wrote:
>>>>>> Add the support for Device tree bindings of extcon-gpio driver.
>>>>>> The extcon-gpio device tree node must include the both 'extcon-id' and
>>>>>> 'gpios' property.
>>>>>
>>>>> I think extcon bindings are a mess in general...
>>>>>
>>>>>> For example:
>>>>>> usb_cable: extcon-gpio-0 {
>>>>>> compatible = "extcon-gpio";
>>>>>> extcon-id = <EXTCON_USB>;
>>>>>> gpios = <&gpio6 1 GPIO_ACTIVE_HIGH>;
>>>>>> }
>>>>>> ta_cable: extcon-gpio-1 {
>>>>>> compatible = "extcon-gpio";
>>>>>> extcon-id = <EXTCON_CHG_USB_DCP>;
>>>>>> gpios = <&gpio3 2 GPIO_ACTIVE_LOW>;
>>>>>> debounce-ms = <50>; /* 50 millisecond */
>>>>>> wakeup-source;
>>>>>> }
>>>>>
>>>>> This is all 1 logical connector, the USB connector. Why are you
>>>>> describing cables? Those are not part of the h/w and are dynamic.
>>>>> Describe this as a connector which is one thing (i.e. node). Use a
>>>>> compatible string that reflects the type of connector
>>>>> (usb-microab-connector), not the driver you want to use. Then define
>>>>> GPIO lines needed to provide state information like VBus, ID, charger
>>>>> modes and control lines like soft connect (D+ pullup enable), VBus
>>>>> enable, etc.
>>>>
>>>> You're right. The extcon-gpio driver will not use the "extcon-gpio" raw compatible.
>>>> As you commented[1], the each connector will have the unique name to use the extcon-gpio.c driver.
>>>> [1] https://lkml.org/lkml/2015/10/21/906
>>>>
>>>>
>>>> For example,
>>>> The extcon-gpio.c driver may have the different name including the h/w information
>>>> according to the kind of external connector.
>>>>
>>>> static const struct of_device_id gpio_extcon_of_match[] = {
>>>> {
>>>> .compatible = "extcon-chg-sdp", /* SDP charger connector */
>>>> .data = EXTCON_CHG_SDP_DATA,
>>>> }, {
>>>> .compatible = "extcon-chg-dcp", /* DCP charger connector */
>>>> .data = EXTCON_CHG_DCP_DATA,
>>>> }, {
>>>> .compatible = "extcon-jack-microphone", /* Microphone jack connector */
>>>> .data = EXTCON_JACK_MICROPHONE_DATA,
>>>> }, {
>>>> .compatible = "extcon-disp-hdmi", /* HDMI connector*/
>>>> .data = EXTCON_DISP_HDMI_DATA,
>>>> },
>>>> ......
>>>> };
>>>
>>> I reply it again.
>>>
>>> The extcon-gpio.c is very similar with existing gpio_keys.c driver[1]
>>> [1] drivers/input/keyboard/gpio_keys.c
>>
>> There is a big difference in that each gpio-key is independent. The
>> only state is pressed or not. A USB connector has multiple pieces of
>> state information. You may be treating them independently, but I don't
>> think they should be.
>
> I think that is it not different because the EXTCON can only notify the whether
> external connector is attached or detached such as gpio-key (pressed or not).
>
> EXTCON don't handle the any additional state except for attached or detached.
>
>>
>>> The gpio_keys.c driver use the following style to support the device-tree.
>>> It use the "gpio-keys" compatible and this dt node include the specific
>>> 'key code' such as 'extcon-id = <EXTCON_CHG_USB_DCP>;'
>>
>> This is state information about what is currently attached. The
>> analogy with gpio-keys would be multiple key codes on one gpio which
>> would be broken...
>
> I compared between 'gpis-keys' and ' extcon-gpio' driver as following:
>
> name | gpio-keys | extcon-gpio
> ---------------------------------------------------------------------------------------------
> gpio | gpios = <> | extcon-gpio = <>
> ---------------------------------------------------------------------------------------------
> type | linux,code = <> | extcon-id = <>
> ---------------------------------------------------------------------------------------------
> key & | KEY_POWER | EXTCON_USB
> extcon id | KEY_VOLUME_UP | EXTCON_CHG_USB_SDP
> | KEY_VOLUME_DOWN | EXTCON_JACK_MICROPHONE
> | etc | etc
> ---------------------------------------------------------------------------------------------
> state | pressed or not | attached or detached
> ---------------------------------------------------------------------------------------------
>
>>
>>>
>>> gpio_keys {
>>> compatible = "gpio-keys";
>>>
>>> power_key {
>>> gpios = <&gpx2 7 GPIO_ACTIVE_LOW>;
>>> linux,code = <KEY_POWER>;
>>> label = "power key";
>>> debounce-interval = <10>;
>>> wakeup-source;
>>> };
>>> };
>>>
>>> If the extcon-gpio.c driver should have the separate compatible according to
>>> the kind of external connector, the list of compatible name of extcon-gpio.c driver
>>> will be increased when new external connector is attached.
>>
>> So? Different h/w needs different compatible strings.
>>
>> But again, you are mixing describing the connector (only what is
>> soldered on a board) and state information (what is attached). Do not
>> put state information into DT (describe the gpio signals or chip that
>> provides the state information).
>>
>>> The extcon-gpio.c driver can separate the kind of external connector
>>> by using the 'extcon-id' property.
>>
>> This use of DT is just broken. Come up with another way.
>>
>> Rob
>
> Thanks,
> Chanwoo Choi
Regards,
Chanwoo Choi
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