linux-kernel - Re: [PATCH 0/3] Add ktd2692 Flash LED driver

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Date:	Tue, 03 Mar 2015 11:55:58 +0900
From:	Ingi Kim <ingi2.kim@...sung.com>
To:	Sakari Ailus <sakari.ailus@....fi>, Bryan Wu <cooloney@...il.com>
Cc:	Jacek Anaszewski <j.anaszewski@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	Thierry Reding <treding@...dia.com>, p.zabel@...gutronix.de,
	Andrew Lunn <andrew@...n.ch>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	florian.vaussard@...l.ch, arno@...isbad.org,
	kuninori.morimoto.gx@...esas.com, hytszk@...il.com,
	antonynpavlov@...il.com,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Linux LED Subsystem <linux-leds@...r.kernel.org>,
	"sw0312.kim@...sung.com" <sw0312.kim@...sung.com>,
	ideal.song@...sung.com
Subject: Re: [PATCH 0/3] Add ktd2692 Flash LED driver

Hi

On 2015년 03월 03일 07:03, Sakari Ailus wrote:
> Hi Bryan,
> 
> On Mon, Mar 02, 2015 at 12:07:42PM -0800, Bryan Wu wrote:
>> On Mon, Mar 2, 2015 at 1:15 AM, Sakari Ailus <sakari.ailus@....fi> wrote:
>>> H Ingi,
>>>
>>> On Mon, Mar 02, 2015 at 04:14:39PM +0900, Ingi Kim wrote:
>>>> Hi Jacek
>>>>
>>>> On 2015년 02월 27일 17:42, Jacek Anaszewski wrote:
>>>>> Hi Ingi,
>>>>>
>>>>> On 02/27/2015 02:01 AM, Ingi Kim wrote:
>>>>>> This patch supports KTD2692 flash LED driver
>>>>>>
>>>>>> Ingi Kim (3):
>>>>>>    of: Add vendor prefix for Kinetic technologies
>>>>>>    leds: ktd2692: add device tree bindings for ktd2692
>>>>>>    leds: Add ktd2692 flash LED driver
>>>>>>
>>>>>>   .../devicetree/bindings/leds/leds-ktd2692.txt      |   19 ++
>>>>>>   .../devicetree/bindings/vendor-prefixes.txt        |    1 +
>>>>>>   drivers/leds/Kconfig                               |    8 +
>>>>>>   drivers/leds/Makefile                              |    1 +
>>>>>>   drivers/leds/leds-ktd2692.c                        |  245 ++++++++++++++++++++
>>>>>>   5 files changed, 274 insertions(+)
>>>>>>   create mode 100644 Documentation/devicetree/bindings/leds/leds-ktd2692.txt
>>>>>>   create mode 100644 drivers/leds/leds-ktd2692.c
>>>>>>
>>>>>
>>>>> In your device tree binding documentation there is torch-gpio mentioned,
>>>>> but you seem not to use it in the driver.
>>>>>
>>>>> We have already LED Flash class (/drivers/leds/led-class-flash.c) for
>>>>> this type of devices, which handles both torch and flash modes
>>>>> (flash_strobe sysfs attribute is provided for strobing the flash).
>>>>>
>>>>> The reference drivers using LED Flash class are still pending [1], but I
>>>>> think that at least leds-aat1290 driver is almost ready for merging.
>>>>> It controls very similar device to yours.
>>>>>
>>>>> Another advantage of using LED Flash class is that it has been designed
>>>>> to be compatible with Video for Linux 2 subsystem, which will allow for registering LED Flash class devices as a V4L2 sub-devices.
>>>>>
>>>>> Adding Sakari.
>>>>>
>>>>
>>>> Ok, I'll check LED Flash class, and add torch-gpio
>>>
>>> Many LED flash chips include a hardware pin for torch control but few really
>>> need it. If you don't, i.e. you can implement the torch using the control bus
>>> instead, I think I'd probably drop it from the chip's DT bindings.
>>>
>>
>> Ingi, please follow Jacek's advice to use LED Flash class interface.
>> I'm reviewing those leds flash drivers and probably merge them soon.
>>
>> Jacek and Sakari thanks for the review.
>>
>> Sakari, so what's the control bus your mentioned here?
> 
> I wasn't cc'd in the original patch so I didn't know whether it was I2C or
> not. Doesn't appear to be.
> 

Thanks for the review and I'll work to use LED Flash class interface
and try adding torch-gpio(flash mode enable) line (I'll rename those gpio lines)

Sakari,
ktd2692 flash led device is controlled through Expresswire single-wire interface
by using the strobe-gpio(control) pin. 


Adding pin information of the KTD2692.

CTRL pin can control LED on/off and Movie/Flash mode current,
Flash timeout, LVP(low voltage protection).

AUX pin(torch-gpio) allows highest priority ON/OFF flash mode control.

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