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

[Jacek Anaszewski <j.anaszewski@samsung.com>]

The documentation being added contains overall description of the
LED Flash Class and the related sysfs attributes.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
---
 Documentation/leds/leds-class-flash.txt |   50 +++++++++++++++++++++++++++++++
 1 file changed, 50 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..82e58b1
--- /dev/null
+++ b/Documentation/leds/leds-class-flash.txt
@@ -0,0 +1,50 @@
+
+Flash LED handling under Linux
+==============================
+
+Some LED devices support two modes - torch and flash. The modes are
+supported by the LED class (see Documentation/leds/leds-class.txt)
+and LED Flash class respectively.
+
+In order to enable 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)
+	- flash_timeout - flash strobe duration in microseconds (RW)
+	- max_flash_timeout - maximum available flash strobe duration (RO)
+	- flash_strobe - flash strobe state (RW)
+	- flash_sync_strobe - one flash device can control more than one
+			      sub-led; when this atrribute is set to 1
+			      the flash led will be strobed synchronously
+			      with the other one controlled by the same
+			      device; flash timeout setting is inherited
+			      from the led being strobed explicitly and
+			      flash brightness setting of a sub-led's
+			      being synchronized is used (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
+
+		Flash faults are cleared by reading the attribute.
-- 
1.7.9.5