Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 USB port LED trigger 2 ==================== 3 4 This LED trigger can be used for signalling to the user a presence of USB device 5 in a given port. It simply turns on LED when device appears and turns it off 6 when it disappears. 7 8 It requires selecting USB ports that should be observed. All available ones are 9 listed as separated entries in a "ports" subdirectory. Selecting is handled by 10 echoing "1" to a chosen port. 11 12 Please note that this trigger allows selecting multiple USB ports for a single 13 LED. This can be useful in two cases: 14 15 1) Device with single USB LED and few physical ports 16 17 In such a case LED will be turned on as long as there is at least one connected 18 USB device. 19 20 2) Device with a physical port handled by few controllers 21 22 Some devices may have one controller per PHY standard. E.g. USB 3.0 physical 23 port may be handled by ohci-platform, ehci-platform and xhci-hcd. If there is 24 only one LED user will most likely want to assign ports from all 3 hubs. 25 26 27 This trigger can be activated from user space on led class devices as shown 28 below: 29 30 echo usbport > trigger 31 32 This adds sysfs attributes to the LED that are documented in: 33 Documentation/ABI/testing/sysfs-class-led-trigger-usbport 34 35 Example use-case: 36 37 echo usbport > trigger 38 echo 1 > ports/usb1-port1 39 echo 1 > ports/usb2-port1 40 cat ports/usb1-port1 41 echo 0 > ports/usb1-port1