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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
