Forwarding this message to the linux-input mailing list, since it concerns the input layer and not the USB layer. Alan Stern PS: Note that problem 1 below is easily solved with a udev script. ----- Forwarded message from Andreas Bergmeier <abergmeier@xxxxxxx> ----- Date: Mon, 17 Oct 2022 18:45:30 +0200 From: Andreas Bergmeier <abergmeier@xxxxxxx> To: linux-usb@xxxxxxxxxxxxxxx Subject: Litra Glow on Linux On my Ubuntu machine i am running 5.15.0. Now when I plugin in my Logitech Litra Glow, it gets detected and the following shows up in my dmesg: ``` input: Logi Litra Glow Consumer Control as /devices/pci0000:00/0000:00:14.0/usb3/3-4/3-4.2/3-4.2:1.0/0003:046D:C900.000B/input/input75 hid-generic 0003:046D:C900.000B: input,hiddev0,hidraw2: USB HID v1.11 Device [Logi Litra Glow] on usb-0000:00:14.0-4.2/input0 ``` Via (hardware) buttons you can switch the device on, regulate the color temperature as well as the brightness. I know of no way to fully control the device from my computer and would like to change that. It seems to me like I need to solve 4 problems (in userspace and maybe kernelspace): 1. Handle plugging in and off 2. Listen to events (button pressed) from the device 3. Get the current state of the device 4. Send events to the device The device seems to provide a pretty bare HID Report interface with no alternate configurations: https://github.com/abergmeier/litra_glow_linux/blob/main/lsusb The HID seems to define 3 Reports: https://github.com/abergmeier/litra_glow_linux/blob/main/parsed_descriptor Ignoring 1. for now. Trying to solve 2. I wrote a basic HIDDEV application. Using `read` I only see events from Report 17 (0x11). For all my experimenting with the device I have never seen a Report 1 or 2. So I get events, but it seems like the provided `hiddev_usage_ref.value` is sometimes wrong (seems to be 0 and 1 for most of the time even if I adjust the brightness). Doing a recording (turning on, adjusting brightness, turning off) of the raw HID events seems like the "correct" events are sent from the device: https://github.com/abergmeier/litra_glow_linux/blob/main/hid-recorder. So it seems to me like maybe the values get mixed up somewhere in the HID code. Alternatively I did a `evtest` run on the /dev/input/event* for the `Logi Litra Glow Consumer Control`: https://github.com/abergmeier/litra_glow_linux/blob/main/evtest When pressing (hardware) buttons no events showed up in `evtest´. Probably not surprising since these would be from Report 1 and 2 IIUC. Now I am not sure whether the USB interface is sketchy or whether one needs to activate the _Consumer Control_ somehow. Trying to solve 3. from what I understand with HID there usually is no way of reading the current state of the device? Trying to solve 4. there are userspace libraries in Python and Go which send events to the device bypassing HID. So there may be some quirks handling necessary in HID but I would defer that until 2. is done. With all that I am pretty much at my wits end and would appreciate any input how to further analyze the device situation. Cheers ----- End forwarded message -----
