linux-kernel - Re: [PATCH RESEND 15/16] leds: add LM3633 driver

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Date:	Mon, 23 Nov 2015 08:40:18 +0900
From:	"Kim, Milo" <milo.kim@...com>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
CC:	<devicetree@...r.kernel.org>, <lee.jones@...aro.org>,
	<linux-kernel@...r.kernel.org>, <linux-leds@...r.kernel.org>
Subject: Re: [PATCH RESEND 15/16] leds: add LM3633 driver

Hi Jacek,

On 11/20/2015 6:22 PM, Jacek Anaszewski wrote:
> On 11/10/2015 08:38 AM, Kim, Milo wrote:
> [...]
>>>> +                cat /sys/class/leds/<led>/pattern_levels
>>>> +                low brightness: 0, high brightness: 255
>>>> +
>>>> +What:        /sys/class/leds/<led>/run_pattern
>>>> +Date:        Oct 2015
>>>> +KernelVersion:    4.3
>>>> +Contact:    Milo Kim <milo.kim@...com>
>>>> +Description:    write only
>>>> +                After 'pattern_times' and 'pattern_levels' are updated,
>>>> +                run the pattern by writing 1 to 'run_pattern'.
>>>> +                To stop running pattern, writes 0 to 'run_pattern'.
>>>
>>> I wonder how registering an in-driver trigger would work. It would
>>> allow for hiding above pattern attributes when the trigger is inactive,
>>> and thus making the sysfs interface more transparent. You could avoid
>>> the need for run_pattern attribute, as setting the trigger would itself
>>> activate the pattern, and setting brightness to 0 would turn it off.
>>
>> I like this idea, let me try to fix it.
>
> After thinking it over, I came to conclusion that implementing it as
> an in-driver trigger is not a proper way to go, since triggers are
> defined as kernel based source of LED events.
>
> This is somehow abused in case of timer trigger which takes hardware
> blinking feature as a first choice and applies software blinking as
> a fallback only. To be consistent with that, we could go for adding
> generic pattern trigger and add a led_pattern_set() API, similarly
> to existing led_blink_set().
>
> The problem is that different LED controllers may implement blinking
> patterns that are configured with different set of parameters. This
> subject would definitely require thorough analysis.
>
> For now, please just expose pattern settings as separate sysfs
> attributes of a LED class device.
>

Thanks for your suggestion.
Then, LM3633 LED driver will support 8 device attributes.

	pattern_time_delay
	pattern_time_rise
	pattern_time_high
	pattern_time_fall
	pattern_time_low
	pattern_brightness_low
	pattern_brightness_high
	pattern_run_pattern

Details will be updated in Documentation/ABI/testing/sysfs-class-led-lm3633.

Best regards,
Milo
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