From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v3] DT: Add documentation for the mfd Maxim max77693 Date: Tue, 31 Mar 2015 12:58:30 +0200 Message-ID: <551A7DD6.8000609@samsung.com> References: <1427709149-15014-1-git-send-email-j.anaszewski@samsung.com> <1427709149-15014-2-git-send-email-j.anaszewski@samsung.com> <20150330115729.GG17971@leverpostej> <55194509.1070008@samsung.com> <20150330132002.GA29200@leverpostej> <20150331091414.GH18321@valkosipuli.retiisi.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <20150331091414.GH18321@valkosipuli.retiisi.org.uk> Sender: linux-leds-owner@vger.kernel.org To: "sakari.ailus@iki.fi" Cc: Mark Rutland , "linux-leds@vger.kernel.org" , "linux-media@vger.kernel.org" , "kyungmin.park@samsung.com" , "pavel@ucw.cz" , "cooloney@gmail.com" , "rpurdie@rpsys.net" , "s.nawrocki@samsung.com" , Andrzej Hajda , Lee Jones , Chanwoo Choi , "devicetree@vger.kernel.org" List-Id: devicetree@vger.kernel.org Hi Sakari, On 03/31/2015 11:14 AM, sakari.ailus@iki.fi wrote: > Hi Mark and Jacek, > > On Mon, Mar 30, 2015 at 02:20:03PM +0100, Mark Rutland wrote: >> Hi, >> >>>>> +Optional properties: >>>>> +- maxim,trigger-type : Flash trigger type. >>>>> + Possible trigger types: >>>>> + LEDS_TRIG_TYPE_EDGE (0) - Rising edge of the signal triggers >>>>> + the flash, >>>>> + LEDS_TRIG_TYPE_LEVEL (1) - Strobe pulse length controls duration >>>>> + of the flash. >>>> >>>> Surely this is required? What should be assumed if this property isn't >>>> present? >>> >>> LEDS_TRIG_TYPE_LEVEL allows for an ISP to do e.g. short flash blink >>> before the actual strobe - it is used for eliminating photographs with >>> closed eyes, or can serve for probing ambient light conditions. >>> >>> With LEDS_TRIG_TYPE_EDGE flash strobe is triggered on rising edge >>> and lasts until programmed timeout expires. >>> >>> This setting is tightly related to a camera sensor, which generates >>> the strobe signal. Effectively it depends on board configuration. >> >> My comment wasn't to do with the semantics of eitehr option but rather >> the optionality of the property. >> >> Surely it's vital to know what this should be, and hence this property >> should be required rather than optional? >> >> If it isn't required, what would the assumed default be? > > I wonder if there's a use case for edge triggering. In level trigger mode, > whichever component generates the trigger signal, determines also the strobe > time (up to the timeout). The sensor or (in the case of lack of the signal > from the sensor) the ISP has the most information on the sensor timing. > > The existing as3654a driver only supports level triggering while the chip > can do edge, too. > > I'd make level default and perhaps add a V4L2 control / sysfs file to change > this if needed. That sounds reasonable. I am going to come up with another version of leds-max77693.c patch anyway, so I'll address this issue too. -- Best Regards, Jacek Anaszewski