This document describes the u-boot status LED API. This allows common u-boot commands to use a board's leds to provide status for activities like booting and downloading files.
Signed-off-by: Tom Rix Tom.Rix@windriver.com --- doc/README.LED | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 78 insertions(+), 0 deletions(-) create mode 100644 doc/README.LED
diff --git a/doc/README.LED b/doc/README.LED new file mode 100644 index 0000000..1221177 --- /dev/null +++ b/doc/README.LED @@ -0,0 +1,78 @@ +Status LED +======================================== + +This README describes the status LED API. + +The API is defined by the include file include/status_led.h + +The first step is to define CONFIG_STATUS_LED in the board config file. + +If the LED support is only for a single board, define CONFIG_BOARD_SPECIFIC_LED +in the board config file. + +At a minimum, these macros must be defined at +STATUS_LED_BIT +STATUS_LED_STATE +STATUS_LED_PERIOD + +If there are multiple status LED's define +STATUS_LED_BIT<n> +STATUS_LED_STATE<n> +STATUS_LED_PERIOD<n> + +Where <n> can a integer 1 through 3. + +STATUS_LED_BIT is passed into the __led_* functions to identify which LED is +being acted on. As such, the value choose must be unique with with respect to +the other STATUS_LED_BIT's. Mapping the value to a physical LED is the +reponsiblity of the __led_* function. + +STATUS_LED_STATE is the initial state of the LED. It should be set to one of +these values: STATUS_LED_OFF or STATUS_LED_ON. + +STATUS_LED_PERIOD is how long is the LED blink period. This usually set to +(CONFIG_SYS_HZ / <N>) where <N> is the frequency of the blink. Typical values +range from 2 to 10. + +Some other LED macros + +STATUS_LED_BOOT is the LED to light when the board is booting. This must be a +valid STATUS_LED_BIT value. + +STATUS_LED_RED is the red LED. It is used signal errors. This must be a valid +STATUS_LED_BIT value. Other similar color LED's are STATUS_LED_YELLOW and +STATUS_LED_BLUE. + +These board must define these functions + +__led_init is called once to initialize the LED to STATUS_LED_STATE. One time +start up code should be placed here. + +__led_set is called to change the state of the LED. + +__led_toggle is called to toggle the current state of the LED. + +Colour LED +======================================== + +Colour LED's are at present only used by ARM. + +The functions names explain their purpose. + +coloured_LED_init +red_LED_on +red_LED_off +green_LED_on +green_LED_off +yellow_LED_on +yellow_LED_off +blue_LED_on +blue_LED_off + +These are weakly defined in lib_arm/board.c to noops. Where applicable, define +these functions in the board specific source. + +TBD : Describe older board dependent macros similar to what is done for +CONFIG_TQM8xxL. + +TBD : Describe general support via asm/status_led.h