LED

Generic LED API provided when a supported compatible is defined in DeviceTree.

To enable support for LEDs, enable the CONFIG_LED Kconfig option.

The most common implementation is for GPIO-connected LEDs. If using GPIO-connected LEDs, enable the LED_GPIO Kconfig option.

LED_BLINK support requires LED driver support and is therefore optional. If LED blink functionality is needed, enable the LED_BLINK Kconfig option. If LED driver doesn’t support HW Blink, SW Blink can be used with the Cyclic framework by enabling the CONFIG_LED_SW_BLINK.

Boot and Activity LEDs are also supported. These LEDs can signal various system operations during runtime, such as boot initialization, file transfers, and flash write/erase operations.

To enable a Boot LED, enable CONFIG_LED_BOOT and define in /options/u-boot root node the property boot-led. This will enable the specified LED to blink and turn ON when the bootloader initializes correctly.

To enable an Activity LED, enable CONFIG_LED_ACTIVITY and define in /options/u-boot root node the property activity-led. This will enable the specified LED to blink and turn ON during file transfers or flash write/erase operations.

Both Boot and Activity LEDs provide a simple API to turn the LED ON or OFF: led_boot_on(), led_boot_off(), led_activity_on(), and led_activity_off().

Both configurations can optionally define a boot/activity-led-period property if CONFIG_LED_BLINK or CONFIG_LED_SW_BLINK is enabled for LED blink operations, which is usually used by the Activity LED. If not defined the default value of 250 (ms) is used.

When CONFIG_LED_BLINK or CONFIG_LED_SW_BLINK is enabled, additional APIs are exposed: led_boot_blink() and led_activity_blink(). Note that if CONFIG_LED_BLINK or CONFIG_LED_SW_BLINK is disabled, these APIs will behave like the led_boot_on() and led_activity_on() APIs, respectively.

structled_uc_plat: Platform data the uclass stores about each device

Definition

struct led_uc_plat {
 const char *label;
 enum led_state_t default_state;
 char name[LED_MAX_NAME_SIZE];
#ifdef CONFIG_LED_SW_BLINK;
 struct led_sw_blink *sw_blink;
#endif;
};

Members

label: LED label
default_state: LED default state
name: LED name, derived from function, color or function-enumerator property.
sw_blink: LED software blink struct

structled_uc_priv: Private data the uclass stores about each device

Definition

struct led_uc_priv {
#ifdef CONFIG_LED_BOOT;
 const char *boot_led_label;
 int boot_led_period;
#endif;
#ifdef CONFIG_LED_ACTIVITY;
 const char *activity_led_label;
 int activity_led_period;
#endif;
};

Members

boot_led_label: Boot LED label
boot_led_period: Boot LED blink period
activity_led_label: Activity LED label
activity_led_period: Activity LED blink period

intled_get_by_label(constchar*label, structudevice **devp): Find an LED device by label

Parameters

const char *label: LED label to look up
struct udevice **devp: Returns the associated device, if found

Return

0 if found, -ENODEV if not found, other -ve on error

intled_set_state(structudevice *dev, enumled_state_tstate): set the state of an LED

Parameters

struct udevice *dev: LED device to change
enum led_state_t state: LED state to set

Return

0 if OK, -ve on error

enumled_state_tled_get_state(structudevice *dev): get the state of an LED

Parameters

struct udevice *dev: LED device to change

Return

LED state led_state_t, or -ve on error

intled_set_period(structudevice *dev, intperiod_ms): set the blink period of an LED

Parameters

struct udevice *dev: LED device to change
int period_ms: LED blink period in milliseconds

Return

0 if OK, -ve on error

intled_bind_generic(structudevice *parent, constchar*driver_name): bind children of parent to given driver

Parameters

struct udevice *parent: Top-level LED device
const char *driver_name: Driver for handling individual child nodes

intled_boot_on(void): turn ON the designated LED for booting

Parameters

void: no arguments

Return

0 if OK, -ve on error

intled_boot_off(void): turn OFF the designated LED for booting

Parameters

void: no arguments

Return

0 if OK, -ve on error

intled_boot_blink(void): turn ON the designated LED for booting

Parameters

void: no arguments

Return

0 if OK, -ve on error

intled_activity_on(void): turn ON the designated LED for activity

Parameters

void: no arguments

Return

0 if OK, -ve on error

intled_activity_off(void): turn OFF the designated LED for activity

Parameters

void: no arguments

Return

0 if OK, -ve on error

intled_activity_blink(void): turn ON the designated LED for activity

Parameters

void: no arguments

Return

0 if OK, -ve on error