Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Userspace LEDs 2 ============== 3 4 The uleds driver supports userspace LEDs. This can be useful for testing 5 triggers and can also be used to implement virtual LEDs. 6 7 8 Usage 9 ===== 10 11 When the driver is loaded, a character device is created at /dev/uleds. To 12 create a new LED class device, open /dev/uleds and write a uleds_user_dev 13 structure to it (found in kernel public header file linux/uleds.h). 14 15 #define LED_MAX_NAME_SIZE 64 16 17 struct uleds_user_dev { 18 char name[LED_MAX_NAME_SIZE]; 19 }; 20 21 A new LED class device will be created with the name given. The name can be 22 any valid sysfs device node name, but consider using the LED class naming 23 convention of "devicename:color:function". 24 25 The current brightness is found by reading a single byte from the character 26 device. Values are unsigned: 0 to 255. Reading will block until the brightness 27 changes. The device node can also be polled to notify when the brightness value 28 changes. 29 30 The LED class device will be removed when the open file handle to /dev/uleds 31 is closed. 32 33 Multiple LED class devices are created by opening additional file handles to 34 /dev/uleds. 35 36 See tools/leds/uledmon.c for an example userspace program.