linux-kernel - Re: [PATCH v6 2/2] leds: rt5033: Add RT5033 Flash led device driver

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Message-id: <565D5277.9080008@samsung.com>
Date:	Tue, 01 Dec 2015 08:55:35 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Ingi Kim <ingi2.kim@...sung.com>
Cc:	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	sameo@...ux.intel.com, lee.jones@...aro.org, rpurdie@...ys.net,
	inki.dae@...sung.com, sw0312.kim@...sung.com,
	beomho.seo@...sung.com, andi.shyti@...sung.com,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org
Subject: Re: [PATCH v6 2/2] leds: rt5033: Add RT5033 Flash led device driver

On 12/01/2015 02:54 AM, Ingi Kim wrote:
> Hi Jacek,
>
> On 2015년 11월 30일 19:59, Jacek Anaszewski wrote:
>> Hi Ingi,
>>
>> On 11/30/2015 03:31 AM, Ingi Kim wrote:
>>> Hi Jacek,
>>>
>>> On 2015년 11월 26일 18:43, Jacek Anaszewski wrote:
>>>> Hi Ingi,
>>>>
>>>> On 11/26/2015 09:02 AM, Ingi Kim wrote:
>>>> [...]
>>>>>>> +torch_unlock:
>>>>>>> +    mutex_unlock(&led->lock);
>>>>>>> +    return ret;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int rt5033_led_flash_brightness_set(struct led_classdev_flash *fled_cdev,
>>>>>>> +                       u32 brightness)
>>>>>>> +{
>>>>>>> +    struct rt5033_sub_led *sub_led = flcdev_to_sub_led(fled_cdev);
>>>>>>> +    struct rt5033_led *led = sub_led_to_led(sub_led);
>>>>>>> +
>>>>>>> +    mutex_lock(&led->lock);
>>>>>>> +    sub_led->flash_brightness = brightness;
>>>>>>> +    mutex_unlock(&led->lock);
>>>>>>
>>>>>> Mutex protection is redundant in this case. You would need it if device
>>>>>> state was also changed here.
>>>>>
>>>>> Okay, I'll remove it.
>>>>>
>>>>>>
>>>>>> BTW why flash brightness can't be written to the device here?
>>>>>>
>>>>>
>>>>> Flash brightness is only affected when FLED flashed (strobing).
>>>>> So, I think it is better to be written in rt5033_led_flash_strobe_set function.
>>>>
>>>> strobe_set op should strobe the flash ASAP, and delegating brightness
>>>> setting there extends a delay between calling strobe_set op
>>>> and actual flash strobe. If you set the brightness here, then you
>>>> wouldn't have to do that in the strobe_set op, of course unless the
>>>> the brightness is altered through the API of the other LED, in two
>>>> separate LEDs case.
>>>>
>>>
>>> The brightness may be able to change its brightness in two separate LEDs case as you see.
>>> So, I think it would be better to write brightness setting in strobe_op.
>>
>> Could you motivate your statement, please? Why would it be better?
>>
>>> In consideration of delay, of course, the brightness is set just when it would be changed.
>>
>> I think that joint iout arrangement will be prevailing - this is the
>> case for your board, isn't it? With the modification I am proposing
>> the gain is clear.
>>
>
> You're right, thanks.
> Did you mean that flash attributes should be written
> on their ops(flash brightness, flash timeout)?

Both in those ops and conditionally in the strobe_set op,
in order to handle two LEDs case, when the other LED has
altered any of the shared settings.

> let me update the driver on your suggestion.
>
>>>>>>> +
>>>>>>> +    return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int rt5033_led_flash_timeout_set(struct led_classdev_flash *fled_cdev,
>>>>>>> +                    u32 timeout)
>>>>>>> +{
>>>>>>> +    struct rt5033_sub_led *sub_led = flcdev_to_sub_led(fled_cdev);
>>>>>>> +    struct rt5033_led *led = sub_led_to_led(sub_led);
>>>>>>> +
>>>>>>> +    mutex_lock(&led->lock);
>>>>>>> +    sub_led->flash_timeout = timeout;
>>>>>>> +    mutex_unlock(&led->lock);
>>>>>>
>>>>>> Ditto.
>>>>>>
>>>>
>>>> Timeout should be also written here.
>>>>
>>>
>>> The timeout may be able to change its flash timeout in two separate LEDs case as you see.
>>> So, I think it would be better to write timeout setting in strobe_op.
>>> In consideration of delay, of course, the timeout is set just when it would be changed.
>>>
>>>> If you will add regmap_write in both ops, then mutex protection will
>>>> have to be preserved, to assure consistency between registers state
>>>> and sub_led->flash_brightness and sub_led->flash_timeout state.
>>>>
>>>
>>> Thanks, but mutex protection is useless in this case.
>>> so I try to remove it.
>>>
>>>>>
>>>>>>> +#define RT5033_FLED_CTRL4_VTRREG_MAX    0x60
>>>>>>
>>>>>> Rename DEF to MASK.
>>>>
>>>> Hmm, here it should be: Rename MAX to MASK.
>>>>
>>>
>>> Oh
>>> Okay, Thanks :)
>>>
>>
>>
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-- 
Best Regards,
Jacek Anaszewski
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