linux-kernel - Re: [PATCH] extcon: ptn5150: add usb role class support

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Date:   Tue, 19 Apr 2022 10:29:57 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Jun Li <jun.li@....com>
Cc:     "myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
        "cw00.choi@...sung.com" <cw00.choi@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Frank Li <frank.li@....com>, Xu Yang <xu.yang_2@....com>
Subject: Re: [PATCH] extcon: ptn5150: add usb role class support

On 19/04/2022 10:23, Jun Li wrote:
> 
> 
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Sent: Tuesday, April 19, 2022 3:57 PM
>> To: Jun Li <jun.li@....com>
>> Cc: myungjoo.ham@...sung.com; cw00.choi@...sung.com;
>> linux-kernel@...r.kernel.org; Frank Li <frank.li@....com>; Xu Yang
>> <xu.yang_2@....com>
>> Subject: Re: [PATCH] extcon: ptn5150: add usb role class support
>>
>> On Tue, 19 Apr 2022 at 09:53, Jun Li <jun.li@....com> wrote:
>>>>>> @@ -132,6 +132,7 @@ config EXTCON_PTN5150
>>>>>>   tristate "NXP PTN5150 CC LOGIC USB EXTCON support"
>>>>>>   depends on I2C && (GPIOLIB || COMPILE_TEST)
>>>>>>   select REGMAP_I2C
>>>>>> + select USB_ROLE_SWITCH
>>>>>
>>>>> You do not need to select it. Driver will work without role
>>>>> switch, won't it? If it works, then probably it should be just imply.
>>>>
>>>> Okay, usb role class provider should enable this for me, will drop it.
>>>
>>> A second check on this and I think I still need this, there maybe some
>>> usb controller driver without usb role switch
>>> + ptn5150 via extcon, so no need USB_ROLE_SWITCH, I need
>>> select it to avoid build break.
>>
>> What build problem exactly? Aren't there stubs for !USB_ROLE_SWITCH case?
> 
> Mostly cases USB_ROLE_SWITCH is enabled, but I cannot 100% ensure
> that, at least I can via make menuconfig change by removing some
> controllers drivers to create a config to generate a build break:
> 
> /opt/fsl-imx-internal-xwayland/5.15-honister/sysroots/x86_64-pokysdk-linux/usr/bin/aarch64-poky-linux/aarch64-poky-linux-ld: drivers/extcon/extcon-ptn5150.o: in function `ptn5150_work_sync_and_put':
> extcon-ptn5150.c:(.text+0x20): undefined reference to `usb_role_switch_put'

This is some old kernel - v5.15. Please test your changes on mainline. I
don't see such issue can happen on a recent kernel - there is an EXPORT
and a stub. Maybe your driver misses proper headers?

Best regards,
Krzysztof