Message-ID: <af17141f-23ae-063d-ade2-42dfdf611d81@gmail.com>
Date:   Fri, 30 Oct 2020 23:34:37 +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 v5 2/2] leds: mt6360: Add LED driver for MT6360

On 10/30/20 9:51 AM, Gene Chen wrote:
> Jacek Anaszewski <jacek.anaszewski@...il.com> 於 2020年10月28日 週三 上午1:28寫道：
>>
>> On 10/27/20 10:28 AM, Gene Chen wrote:
>>> Jacek Anaszewski <jacek.anaszewski@...il.com> 於 2020年10月21日 週三 上午5:47寫道：
>>>>
>>>> On 10/20/20 8:44 AM, Gene Chen wrote:
>>>>> Jacek Anaszewski <jacek.anaszewski@...il.com> 於 2020年10月9日 週五 上午5:51寫道：
>>>>>>
>>>>>> Hi Gene,
>>>>>>
>>>>>> On 10/7/20 3:42 AM, Gene Chen wrote:
>>>>>>> From: Gene Chen <gene_chen@...htek.com>
>>>>>>>
>>>>>>> Add MT6360 LED driver include 2-channel Flash LED with torch/strobe mode,
>>>>>>> 3-channel RGB LED support Register/Flash/Breath Mode, and 1-channel for
>>>>>>> moonlight LED.
>>>>>>>
>>>>>>> Signed-off-by: Gene Chen <gene_chen@...htek.com>
>>>>>>> ---
>>>>>>>      drivers/leds/Kconfig       |  12 +
>>>>>>>      drivers/leds/Makefile      |   1 +
>>>>>>>      drivers/leds/leds-mt6360.c | 783 +++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>      3 files changed, 796 insertions(+)
>>>>>>>      create mode 100644 drivers/leds/leds-mt6360.c
>>>>>>>
>>>>>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>>>>>> index 1c181df..c7192dd 100644
>>>>>>> --- a/drivers/leds/Kconfig
>>>>>>> +++ b/drivers/leds/Kconfig
>>>>>>> @@ -271,6 +271,18 @@ config LEDS_MT6323
>>>>>>>            This option enables support for on-chip LED drivers found on
>>>>>>>            Mediatek MT6323 PMIC.
>>>>>>>
>>>>>>> +config LEDS_MT6360
>>>>>>> +     tristate "LED Support for Mediatek MT6360 PMIC"
>>>>>>> +     depends on LEDS_CLASS_FLASH && OF
>>>>>>> +     depends on LEDS_CLASS_MULTICOLOR
>>>>>>
>>>>>> Since CONFIG_LED_CLASS_MULTICOLOR can be turned off you need to have
>>>>>> below instead:
>>>>>>
>>>>>> depends on LEDS_CLASS_MULTICOLOR || !!LEDS_CLASS_MULTICOLOR
>>
>> My typo here, should be one "!":
>>
>> depends on LEDS_CLASS_MULTICOLOR || !LEDS_CLASS_MULTICOLOR
>>
>> And you should also have
>>
>> depends on LEDS_CLASS_FLASH || !LEDS_CLASS_FLASH
>>
>> But to make it work correctly you would have to add registration
>> stubs to include/linux/led-class-flash.h similarly to LED mc stubs
>> in include/linux/led-class-multicolor.h.
>>
>>>>>>
>>>>>> Unless you want to prevent enabling the driver without RGB LED,
>>>>>> but that does not seem to be reasonable at first glance.
>>>>>>
>>>>>
>>>>> May I change to "select LEDS_CLASS_MULTICOLOR"?
>>>>> I suppose RGB always use multicolor mode.
>>>>
>>>> You will also have moonlight LED that will not need multicolor
>>>> framework. Is it somehow troublesome to keep "depends on"?
>>>>
>>>
>>> If only use ML LED and FLED,  DTSI will only define ML LED and FLED.
>>> Therefore, the drivers probe will not register rgb multicolor device.
>>
>> Please test your use case again with my fixed "depends on".
>>
>> In case when there is only ML LED and FLED in the DT it should
>> register both devices if LEDS_CLASS_FLASH is turned on.
>> Multicolor framework has nothing to do in this case.
>>
>> But if you additionally had MC LED node, then it should
>> be registered only if LEDS_CLASS_MULTICOLOR is enabled.
>>
>> Similarly, when FLED node is present, but LEDS_CLASS_FLASH
>> is off, and LEDS_CLASS_MULTICOLOR is on, the driver should still
>> compile, but register only LED MC device (if its node is present).
>>
> 
> I think this case only register LED device, not LED "MC" device.
> Because our FLASH is not a multicolor device.

No, here I was describing following setup:

- DT FLED node is present, CONFIG_LEDS_CLASS_FLASH is off
- DT MC node is present, CONFIG_LEDS_CLASS_MULTICOLOR is on

ML LED presence in DT is irrelevant in this case.
It should be always registered if there is corresponding DT node
and LEDS_CLASS is on.

> 
>> Possible should be also the case when both LEDS_CLASS_FLASH
>> and LEDS_CLASS_MULTICOLOR are off. Then only LED class device
>> for ML LED will be registered (provided there is ML DT node).
>> But to make it possible you should have also "depends on LEDS_CLASS"
>> in the Kconfig entry.
>>
> 
> According to your suggestion,
> depends on LED_CLASS && LEDS_CLASS_FLASH && OF

s/LED_CLASS/LEDS_CLASS/

And you have to remove LEDS_CLASS_FLASH from above line.

> depends on LEDS_CLASS_MULTICOLOR || !!LEDS_CLASS_MULTICOLOR

s/!!LEDS_CLASS_MULTICOLOR/!LEDS_CLASS_MULTICOLOR/

> depends on LEDS_CLASS_FLASH || !LEDS_CLASS_FLASH
> depends on MFD_MT6360

You will need V4L2_FLASH_LED_CLASS dependency as well, to avoid
build break, when it is set to 'm'.

To recap, following block of dependencies is required:

depends on LEDS_CLASS && OF
depends on LEDS_CLASS_MULTICOLOR || !LEDS_CLASS_MULTICOLOR
depends on LEDS_CLASS_FLASH || !LEDS_CLASS_FLASH
depends on V4L2_FLASH_LED_CLASS || !V4L2_FLASH_LED_CLASS
depends on MFD_MT6360

> 
> and source code add constraint
> 
> #if IS_ENABLED(CONFIG_LEDS_CLASS_MULTICOLOR)
>      ret = devm_led_classdev_multicolor_register_ext(parent, &led->rgb,
> init_data);
> #endif
> 
> #if IS_ENABLED(CONFIG_LEDS_CLASS_FLASH)
>      ret = devm_led_classdev_flash_register_ext(parent, &led->flash, init_data);
> #endif

No, the guards should be in headers. That's why I recommended adding
no ops for LED flash class registration functions in previous email.

Please compare include/linux/led-class-multicolor.h and do similar 
changes in include/linux/led-class-flash.h.

> =============
> 
> Or Should I seperate two drivers?
> one for RGB LED, one for ML LED and FLED

This would incur unnecessary code duplication.

-- 
Best regards,
Jacek Anaszewski

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