linux-kernel - Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension

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Message-id: <5486F5A0.9060700@samsung.com>
Date:	Tue, 09 Dec 2014 14:14:08 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Sakari Ailus <sakari.ailus@....fi>
Cc:	linux-leds@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	b.zolnierkie@...sung.com, pavel@....cz, cooloney@...il.com,
	rpurdie@...ys.net, s.nawrocki@...sung.com, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org
Subject: Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED
 Flash class extension

Hi Sakari,

On 12/09/2014 01:38 PM, Sakari Ailus wrote:

[...]

>>> How does the user btw. figure out which flash LEDs may be strobed
>>> synchronously using the LED flash interface?
>>
>> The flash_sync_strobe argument is absent if synchronized strobe
>> is not available for a LED. The driver defines this by setting
>> newly added LED_DEV_CAP_COMPOUND flag.
>
> I meant that how does the user figure out which LEDs may be strobed
> synchronously, together. Say, if you have two of these chips and four LEDs,
> then how does it work? :-)
>

User can figure it out by checking the existence of the
flash_sync_strobe attribute. Sub-leds can by synchronized only
when are driven by common chip. It is assumed that sub-leds of
one chip will have common segment in their name, defined in
DT 'label' property. Maybe we should enforce it by adding another
property to the leds/common.txt DT binding, e.g. 'device-prefix'?

Best Regards,
Jacek Anaszewski

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