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Date:	Thu, 20 Mar 2014 15:51:05 +0100
From:	Jacek Anaszewski <>
	Jacek Anaszewski <>,
	Bryan Wu <>,
	Richard Purdie <>
Subject: [PATCH/RFC 3/8] Documentation: leds: Add description of flash mode

Signed-off-by: Jacek Anaszewski <>
Acked-by: Kyungmin Park <>
Cc: Bryan Wu <>
Cc: Richard Purdie <>
 Documentation/leds/leds-class.txt |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt
index 62261c0..d34d990 100644
--- a/Documentation/leds/leds-class.txt
+++ b/Documentation/leds/leds-class.txt
@@ -8,6 +8,31 @@ LED is defined in max_brightness file. The brightness file will set the brightne
 of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware
 brightness support so will just be turned on for non-zero brightness settings.
+Some LED devices support two modes - torch and flash. A LED subsystem device
+driver can declare this by calling led_classdev_init_flash function and
+initializing flash field of the led_classdev structure (see <linux/leds.h>).
+There are five sysfs attributes dedicated specifically to the flash LED devices:
+	- flash_mode - sets/unsets the flash mode
+	- flash_timeout - determines duration of the flash blink in milliseconds
+	- max_flash_timeout - maximum flash blink duration that can be set (RO)
+	- flash_fault - bitmask of flash faults that may have occured, 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.
+	- hw_triggered - Some devices expose dedicated hardware pins for
+			 triggering a flash LED. The attribute allows to set
+			 this mode. After writting 1 the brightness has to be set
+			 to the desired value to arm a led.
 The class also introduces the optional concept of an LED trigger. A trigger
 is a kernel based source of led events. Triggers can either be simple or
 complex. A simple trigger isn't configurable and is designed to slot into

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