linux-kernel - Re: [PATCH v7 1/5] leds: flash: Add flash registration with undefined CONFIG_LEDS_CLASS

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Message-ID: <5c4a5780-afec-fa7f-307e-b969192ec677@gmail.com>
Date:   Mon, 23 Nov 2020 22:06:57 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Gene Chen <gene.chen.richtek@...il.com>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Dan Murphy <dmurphy@...com>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Gene Chen <gene_chen@...htek.com>, Wilma.Wu@...iatek.com,
        shufan_lee@...htek.com, cy_huang@...htek.com,
        benjamin.chao@...iatek.com
Subject: Re: [PATCH v7 1/5] leds: flash: Add flash registration with undefined
 CONFIG_LEDS_CLASS_FLASH

On 11/23/20 4:20 AM, Gene Chen wrote:
> Jacek Anaszewski <jacek.anaszewski@...il.com> 於 2020年11月20日 週五 上午6:29寫道：
>>
>> Hi Gene,
>>
>> On 11/18/20 11:47 AM, Gene Chen wrote:
>>> From: Gene Chen <gene_chen@...htek.com>
>>>
>>> Add flash registration with undefined CONFIG_LEDS_CLASS_FLASH
>>>
>>> Signed-off-by: Gene Chen <gene_chen@...htek.com>
>>> ---
>>>    include/linux/led-class-flash.h | 36 ++++++++++++++++++++++++++++++++++++
>>>    1 file changed, 36 insertions(+)
>>>
>>> diff --git a/include/linux/led-class-flash.h b/include/linux/led-class-flash.h
>>> index 21a3358..4f56c28 100644
>>> --- a/include/linux/led-class-flash.h
>>> +++ b/include/linux/led-class-flash.h
>>> @@ -85,6 +85,7 @@ static inline struct led_classdev_flash *lcdev_to_flcdev(
>>>        return container_of(lcdev, struct led_classdev_flash, led_cdev);
>>>    }
>>>
>>> +#if IS_ENABLED(CONFIG_LEDS_CLASS_FLASH)
>>>    /**
>>>     * led_classdev_flash_register_ext - register a new object of LED class with
>>>     *                               init data and with support for flash LEDs
>>> @@ -127,6 +128,41 @@ static inline int devm_led_classdev_flash_register(struct device *parent,
>>>    void devm_led_classdev_flash_unregister(struct device *parent,
>>>                                        struct led_classdev_flash *fled_cdev);
>>>
>>> +#else
>>> +
>>> +static inline int led_classdev_flash_register_ext(struct device *parent,
>>> +                                 struct led_classdev_flash *fled_cdev,
>>> +                                 struct led_init_data *init_data)
>>> +{
>>> +     return -EINVAL;
>>
>> s/-EINVAL/0/
>>
>> The goal here is to assure that client will not fail when using no-op.
>>
>>> +}
>>> +
>>> +static inline int led_classdev_flash_register(struct device *parent,
>>> +                                        struct led_classdev_flash *fled_cdev)
>>> +{
>>> +     return led_classdev_flash_register_ext(parent, fled_cdev, NULL);
>>> +}
>>
>> This function should be placed after #ifdef block because its
>> shape is the same for both cases.
>>
>>> +static inline void led_classdev_flash_unregister(struct led_classdev_flash *fled_cdev) {};
>>> +static inline int devm_led_classdev_flash_register_ext(struct device *parent,
>>> +                                  struct led_classdev_flash *fled_cdev,
>>> +                                  struct led_init_data *init_data)
>>> +{
>>> +     return -EINVAL;
>>
>> /-EINVAL/0/
>>
>> Please do the same fix in all no-ops in the led-class-multicolor.h,
>> as we've discussed.
>>
> 
> I think return -EINVAL is correct, because I should register flash
> light device if I define FLED in DTS node.

I don't quite follow your logic here.

No-op function's purpose is to simplify the code on the caller's side.
Therefore it should report success.

Please return 0 from it.

-- 
Best regards,
Jacek Anaszewski