Reading through hid-input it seems like the custom Usage Page of Logitech gets explicity ignored. So for Brightness and/or Color Temperature controls I wonder whether it would be appropriate to map these to ABS_WHEEL. On Wed, 19 Oct 2022 at 17:17, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > 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 `evtestด. > 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 -----
