From f98e0640c5c6b8bb00336dae8d06ede862754c28 Mon Sep 17 00:00:00 2001 From: Bastien Nocera Date: Thu, 2 Mar 2023 11:55:53 +0100 Subject: USB: core: Add wireless_status sysfs attribute MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a wireless_status sysfs attribute to USB devices to keep track of whether a USB device that's comprised of a receiver dongle and an emitter device over a, most of the time proprietary, wireless link has its emitter connected or disconnected. This will be used by user-space OS components to determine whether the battery-powered part of the device is wirelessly connected or not, allowing, for example: - upower to hide the battery for devices where the device is turned off but the receiver plugged in, rather than showing 0%, or other values that could be confusing to users - Pipewire to hide a headset from the list of possible inputs or outputs or route audio appropriately if the headset is suddenly turned off, or turned on - libinput to determine whether a keyboard or mouse is present when its receiver is plugged in. This is done at the USB interface level as: - the interface on which the wireless status is detected is sometimes not the same as where it could be consumed (eg. the audio interface on a headset dongle will still appear even if the headset is turned off), and we cannot have synchronisation of status across subsystems. - this behaviour is not specific to HID devices, even if the protocols used to determine whether or not the remote device is connected can be HID. This is not an attribute that is meant to replace protocol specific APIs, such as the ones available for WWAN, WLAN/Wi-Fi, or Bluetooth or any other sort of networking, but solely for wireless devices with an ad-hoc “lose it and your device is e-waste” receiver dongle. The USB interface will only be exporting the wireless_status sysfs attribute if it gets set through the API exported in the next commit. Signed-off-by: Bastien Nocera Acked-by: Greg Kroah-Hartman Acked-by: Alan Stern Link: https://lore.kernel.org/r/20230302105555.51417-4-hadess@hadess.net Signed-off-by: Benjamin Tissoires --- Documentation/ABI/testing/sysfs-bus-usb | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index 545c2dd97ed0..cb172db41b34 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -166,6 +166,23 @@ Description: The file will be present for all speeds of USB devices, and will always read "no" for USB 1.1 and USB 2.0 devices. +What: /sys/bus/usb/devices//wireless_status +Date: February 2023 +Contact: Bastien Nocera +Description: + Some USB devices use a USB receiver dongle to communicate + wirelessly with their device using proprietary protocols. This + attribute allows user-space to know whether the device is + connected to its receiver dongle, and, for example, consider + the device to be absent when choosing whether to show the + device's battery, show a headset in a list of outputs, or show + an on-screen keyboard if the only wireless keyboard is + turned off. + This attribute is not to be used to replace protocol specific + statuses available in WWAN, WLAN/Wi-Fi, Bluetooth, etc. + If the device does not use a receiver dongle with a wireless + device, then this attribute will not exist. + What: /sys/bus/usb/devices/...//port Date: August 2012 Contact: Lan Tianyu -- cgit v1.2.3