On Tue, Jan 17, 2023 at 04:17:23PM +0100, Bastien Nocera wrote: > Hey, > > TLDR: new sysfs attribute that makes it possible to leave receivers for > wireless headsets plugged in. At the USB level, or at the base driver > level? > > Longer version: > I started working on implementing support for some wireless headsets > that use USB receivers to communicate to the headset itself. > > The USB receivers have multiple interfaces, and independent drivers for > each, as is wont to do for USB devices. There's usually a HID interface > to do the custom stuff (LEDs, battery status, connection status, etc.) > and a standard audio class interface. > > Those drivers don't know anything about each other, and getting them to > talk to each other would be rather complicated. Additionally the audio > interface is still somewhat functional when the headset is > disconnected. > > In the end, I came up with this new sysfs attribute that would make it > possible for user-space (PulseAudio or Pipewire) to know whether the > receiver is plugged in or not. > > That allows user-space to not show the battery information for the > device (rather than 0 percent), not offer the headset as an output, and > potentially automatically switch to it when the headset is powered on. > > The question is whether this should be a USB sysfs attribute, or one at > the base driver level. Example implementation of the USB sysfs > attribute itself below. Do you know of any non-USB devices using the receiver/emitter approach? > I have a patch for a USB API as well, but I'm having some problems > creating deferred work on a soft irq. > > Cheers > > ---- > Add a wireless_status sysfs attribute to USB devices to keep track of > whether a USB device that uses a receiver/emitter combo has its > emitter connected or disconnected. > > By default, the USB device will declare not to use a receiver/emitter. How do you plan to tell which devices do use a receiver/emitter? Is this something the drivers already knowo about? Is it conceivable that a single device might have more than one receiver? If so, should the attribute belong to an interface rather than to the USB device? Alan Stern
