uboot/doc/README.LED
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   1Status LED
   2========================================
   3
   4This README describes the status LED API.
   5
   6The API is defined by the include file include/status_led.h
   7
   8The first step is to enable CONFIG_LED_STATUS in menuconfig:
   9> Device Drivers > LED Support.
  10
  11If the LED support is only for specific board, enable
  12CONFIG_LED_STATUS_BOARD_SPECIFIC in the menuconfig.
  13
  14Status LEDS 0 to 5 are enabled by the following configurations at menuconfig:
  15CONFIG_STATUS_LED0, CONFIG_STATUS_LED1, ... CONFIG_STATUS_LED5
  16
  17The following should be configured for each of the enabled LEDs:
  18CONFIG_STATUS_LED_BIT<n>
  19CONFIG_STATUS_LED_STATE<n>
  20CONFIG_STATUS_LED_FREQ<n>
  21Where <n> is an integer 1 through 5 (empty for 0).
  22
  23CONFIG_STATUS_LED_BIT is passed into the __led_* functions to identify which LED
  24is being acted on. As such, the value choose must be unique with with respect to
  25the other CONFIG_STATUS_LED_BIT's. Mapping the value to a physical LED is the
  26reponsiblity of the __led_* function.
  27
  28CONFIG_STATUS_LED_STATE is the initial state of the LED. It should be set to one
  29of these values: CONFIG_LED_STATUS_OFF or CONFIG_LED_STATUS_ON.
  30
  31CONFIG_STATUS_LED_FREQ determines the LED blink frequency.
  32Values range from 2 to 10.
  33
  34Some other LED macros
  35---------------------
  36
  37CONFIG_STATUS_LED_BOOT is the LED to light when the board is booting.
  38This must be a valid LED number (0-5).
  39
  40CONFIG_STATUS_LED_RED is the red LED. It is used to signal errors. This must be
  41a valid LED number (0-5). Other similar color LED's macros are
  42CONFIG_STATUS_LED_GREEN, CONFIG_STATUS_LED_YELLOW and CONFIG_STATUS_LED_BLUE.
  43
  44General LED functions
  45---------------------
  46The following functions should be defined:
  47
  48__led_init is called once to initialize the LED to CONFIG_STATUS_LED_STATE.
  49One time start up code should be placed here.
  50
  51__led_set is called to change the state of the LED.
  52
  53__led_toggle is called to toggle the current state of the LED.
  54
  55Colour LED
  56========================================
  57
  58Colour LED's are at present only used by ARM.
  59
  60The functions names explain their purpose.
  61
  62coloured_LED_init
  63red_LED_on
  64red_LED_off
  65green_LED_on
  66green_LED_off
  67yellow_LED_on
  68yellow_LED_off
  69blue_LED_on
  70blue_LED_off
  71
  72These are weakly defined in arch/arm/lib/board.c to noops. Where applicable, define
  73these functions in the board specific source.
  74
  75TBD : Describe older board dependent macros similar to what is done for
  76
  77TBD : Describe general support via asm/status_led.h
  78