From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH/RFC v7 3/3] Documentation: leds: Add description of LED Flash Class extension Date: Fri, 14 Nov 2014 11:21:35 +0100 Message-ID: <5465D7AF.9010903@samsung.com> References: <1415808557-29557-1-git-send-email-j.anaszewski@samsung.com> <1415808557-29557-4-git-send-email-j.anaszewski@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mailout4.w1.samsung.com ([210.118.77.14]:62741 "EHLO mailout4.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965115AbaKNKVk (ORCPT ); Fri, 14 Nov 2014 05:21:40 -0500 In-reply-to: Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Bryan Wu Cc: Linux LED Subsystem , "linux-media@vger.kernel.org" , sakari.ailus@linux.intel.com, Kyungmin Park , b.zolnierkie@samsung.com, Richard Purdie Hi Bryan, Thanks for a review. On 11/13/2014 07:58 PM, Bryan Wu wrote: > On Wed, Nov 12, 2014 at 8:09 AM, Jacek Anaszewski > wrote: >> The documentation being added contains overall description of the >> LED Flash Class and the related sysfs attributes. >> >> Signed-off-by: Jacek Anaszewski >> Acked-by: Kyungmin Park >> Cc: Bryan Wu >> Cc: Richard Purdie >> --- >> Documentation/leds/leds-class-flash.txt | 39 +++++++++++++++++++++++++++++++ >> 1 file changed, 39 insertions(+) >> create mode 100644 Documentation/leds/leds-class-flash.txt >> >> diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt >> new file mode 100644 >> index 0000000..0164329 >> --- /dev/null >> +++ b/Documentation/leds/leds-class-flash.txt >> @@ -0,0 +1,39 @@ >> + >> +Flash LED handling under Linux >> +============================== >> + >> +Some LED devices support two modes - torch and flash. In order to enable > > I think I asked this question before, Torch, Flash and Indicator. As > you answered torch is implemented by sync led brightness set operation > in our LEDS_CLASS and Flash is implemented in this LEDS_CLASS_FLASH. > > I suggest put this information in document or code comments. Then > people know how to use torch and flash. Good point. > For indicator I still don't know why we need this since indicator is > like blinking and it should be support by LEDS_CLASS right? Indicator led is strictly related to flash devices. It is also called a "privacy led" because of its purpose - protecting a privacy of a person being recorded by providing a light signal signifying that a camera is on. It is a low current led, but some devices use the same led as for torch and flash and only apply reduced current in the indicator mode. In the V4L2 subsystem I see only one driver supporting indicator leds: /drivers/media/i2c/as3645a.c. It looks like indicator intensity can be set only when flash mode is V4L2_FLASH_LED_MODE_NONE, i.e. torch and flash leds cannot be active simultaneously with indicator led. It is reasonable, as active torch led is a sufficient signalization of recording. In the LED subsystem I also see indicators in some drivers, e.g. leds-lm355x.c, but they are registered as a separate LED class devices. Moreover the driver adds also a "pattern" sysfs attribute for choosing indicator blinking pattern so that is something to be added to the LED Flash class. I think that similar improvement to the V4L2 Flash API should be made. Sakari, what is your opinion? > Flash is for some camera capture, right? > >> +support for flash LEDs CONFIG_LEDS_CLASS_FLASH symbol must be defined >> +in the kernel config. A flash LED driver must register in the LED subsystem >> +with led_classdev_flash_register to gain flash capabilities. >> + >> +Following sysfs attributes are exposed for controlling flash led devices: >> + >> + - flash_brightness - flash LED brightness in microamperes (RW) >> + - max_flash_brightness - maximum available flash LED brightness (RO) >> + - indicator_brightness - privacy LED brightness in microamperes (RW) >> + - max_indicator_brightness - maximum privacy LED brightness in >> + microamperes (RO) > > What's the privacy mean here? Indeed, consistent naming should be applied, so I will modify it to: "maximum indicator LED brightness in microaperes (RO)" >> + - flash_timeout - flash strobe duration in microseconds (RW) >> + - max_flash_timeout - maximum available flash strobe duration (RO) >> + - flash_strobe - flash strobe state (RW) >> + - flash_fault - bitmask of flash faults that may have occurred, >> + possible flags are: >> + * 0x01 - flash controller voltage to the flash LED has exceeded >> + the limit specific to the flash controller >> + * 0x02 - the flash strobe was still on when the timeout set by >> + the user has expired; not all flash controllers may >> + set this in all such conditions >> + * 0x04 - the flash controller has overheated >> + * 0x08 - the short circuit protection of the flash controller >> + has been triggered >> + * 0x10 - current in the LED power supply has exceeded the limit >> + specific to the flash controller >> + * 0x40 - flash controller voltage to the flash LED has been >> + below the minimum limit specific to the flash >> + * 0x80 - the input voltage of the flash controller is below >> + the limit under which strobing the flash at full >> + current will not be possible. The condition persists >> + until this flag is no longer set >> + * 0x100 - the temperature of the LED has exceeded its allowed >> + upper limit > > Are these error code the same for all the LED controller? Or just for > some specific chip? They are generic error codes, and map directly to V4L2 Flash errors. Error descriptions were copied from the V4L2 Flash documentation. Best Regards, Jacek Anaszewski