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

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Message-ID: <CAE+NS36yU_ho5eV=j2rd36XqGXBKj3d8KP-bsrCCnWvxzV3Afw@mail.gmail.com>
Date:   Tue, 24 Nov 2020 14:08:19 +0800
From:   Gene Chen <gene.chen.richtek@...il.com>
To:     Jacek Anaszewski <jacek.anaszewski@...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

Jacek Anaszewski <jacek.anaszewski@...il.com> 於 2020年11月24日 週二 上午5:07寫道：
>
> 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.
>

Just like those functions in led-class-multicolor.h, caller may use
return value to check whether FLED is registered successfully or not.
For this case, is returning 0 a little bit misleading?

> --
> Best regards,
> Jacek Anaszewski