linux-kernel - Re: [PATCH v3 1/2] leds: mt6360: Add LED driver for MT6360

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Message-ID: <7ce924da-5119-0406-7995-560c32097040@gmail.com>
Date:   Thu, 10 Sep 2020 22:31:28 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Gene Chen <gene.chen.richtek@...il.com>, robh+dt@...nel.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Dan Murphy <dmurphy@...com>, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, 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 v3 1/2] leds: mt6360: Add LED driver for MT6360

On 9/10/20 10:25 PM, Pavel Machek wrote:
> Hi!
> 
>>>> 1. set FLED1 brightness
>>>> # echo 1 > /sys/class/leds/white:flash1/flash_brightness
>>>> 2. enable FLED1 strobe
>>>> # echo 1 > /sys/class/leds/white:flash1/flash_strobe
>>>> 3 . turn off FLED1 strobe (just used to gaurantee the strobe mode
>>>> flash leds must be turned off)
>>>> # echo 0 > /sys/class/leds/white:flash1/flash_strobe
>>>
>>> I believe I'd preffer only exposing torch functionality in
>>> /sys/class/leds. .. strobe can be supported using v4l2 APIs.
>>
>> Actually having LED flash class without strobe is pointless.
>> If you looked at led_classdev_flash_register_ext() you would see that
>> it fails with uninitialized strobe_set op. And V4L2 API for strobing
>> flash calls strobe_set from LED flash class beneath.
>>
>> That was the idea behind LED and V4L2 flash API unification - there
>> is one hardware driver needed, the V4L2 Flash layer just takes over
>> control over it when needed.
> 
> I agree that one driver is enough.
> 
> But we should not need flash_strobe file in sysfs. Simply use V4L2 for
> that.

Apart from the fact that we can't remove it from LED flash class ABI
now, why would you like to prevent the user from exploiting main feature
of the hardware?

-- 
Best regards,
Jacek Anaszewski