Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/Documentation/leds/ledtrig-usbport.rst b/Documentation/leds/ledtrig-usbport.rst
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+====================
+USB port LED trigger
+====================
+
+This LED trigger can be used for signalling to the user a presence of USB device
+in a given port. It simply turns on LED when device appears and turns it off
+when it disappears.
+
+It requires selecting USB ports that should be observed. All available ones are
+listed as separated entries in a "ports" subdirectory. Selecting is handled by
+echoing "1" to a chosen port.
+
+Please note that this trigger allows selecting multiple USB ports for a single
+LED.
+
+This can be useful in two cases:
+
+1) Device with single USB LED and few physical ports
+====================================================
+
+In such a case LED will be turned on as long as there is at least one connected
+USB device.
+
+2) Device with a physical port handled by few controllers
+=========================================================
+
+Some devices may have one controller per PHY standard. E.g. USB 3.0 physical
+port may be handled by ohci-platform, ehci-platform and xhci-hcd. If there is
+only one LED user will most likely want to assign ports from all 3 hubs.
+
+
+This trigger can be activated from user space on led class devices as shown
+below::
+
+  echo usbport > trigger
+
+This adds sysfs attributes to the LED that are documented in:
+Documentation/ABI/testing/sysfs-class-led-trigger-usbport
+
+Example use-case::
+
+  echo usbport > trigger
+  echo 1 > ports/usb1-port1
+  echo 1 > ports/usb2-port1
+  cat ports/usb1-port1
+  echo 0 > ports/usb1-port1