[PATCH/RFC v10 02/19] Documentation: leds: Add description of LED Flash class extension

[Jacek Anaszewski]

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

Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Bryan Wu <cooloney@xxxxxxxxx>
Cc: Richard Purdie <rpurdie@xxxxxxxxx>
---
 Documentation/leds/leds-class-flash.txt |   57 +++++++++++++++++++++++++++++++
 1 file changed, 57 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..d80096b
--- /dev/null
+++ b/Documentation/leds/leds-class-flash.txt
@@ -0,0 +1,57 @@
+
+Flash LED handling under Linux
+==============================
+
+Some LED devices support two modes - torch and flash. In the LED subsystem
+those modes are supported by LED class (see Documentation/leds/leds-class.txt)
+and LED Flash class respectively. The torch mode related features are enabled
+by default and the flash ones only if a driver declares it by setting
+LED_DEV_CAP_FLASH flag.
+
+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 function to gain flash
+related capabilities.
+
+There are flash LED devices which can control more than one LED and allow for
+strobing the sub-leds synchronously. A LED will be strobed synchronously with
+the one whose identifier is written to the flash_sync_strobe sysfs attribute.
+The list of available sub-led identifiers can be read from the available_sync_leds
+sysfs attribute. In order to enable the related settings the driver must set
+LED_DEV_CAP_SYNC_STROBE flag.
+
+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)
+	- available_sync_leds - list of sub-leds available for flash strobe
+				synchronization (RO)
+	- flash_sync_strobe - identifier of the sub-led to synchronize the flash
+			      strobe with; 0 stands for no synchronization (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
+		* 0x20 - the flash controller has detected a short or open
+			 circuit condition on the indicator LED
+		* 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, if possible, by reading the attribute.
-- 
1.7.9.5

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