On Oct 01 2024, Werner Sembach wrote: > Hi Armin, > > Am 01.10.24 um 18:45 schrieb Armin Wolf: [...snipped...] > > Why not having a simple led driver for HID LampArray devices which exposes the > > whole LampArray as a single LED? > Yes that is my plan, but see my last reply to Benjamin, it might not be > trivial as different leds in the same LampArray might have different max > values for red, green, blue, and intensity. And the LampArray spec even > allows to mix RGB and non-RGB leds. > > > > If userspace wants to have direct control over the underlying LampArray device, > > it just needs to unbind the default driver (maybe udev can be useful here?). > There was something in the last discussion why this might not work, but i > can't put my finger on it. We recently have the exact same problem, so it's still fresh in my memory. And here are what is happening: - you can unbind the driver with a sysfs command for sure - but then the device is not attached to a driver so HID core doesn't expose the hidraw node - you'd think "we can just rebind it to hid-generic", but that doesn't work because hid-generic sees that there is already a loaded driver that can handle the device and it'll reject itself because it gives priority over the other driver - what works is that you might be able to unload the other driver, but if it's already used by something else (like hid-multitouch), you don't want to do that. And also if you unload that driver, whenever the driver gets re-inserted, hid-generic will unbind itself, so back to square one So unless we find a way to forward the "manual" binding to hid-generic, and/or we can also quirk the device with HID_QUIRK_IGNORE_SPECIAL_DRIVER[0] just unbinding the device doesn't work. Cheers, Benjamin PS: brain fart: if HID LampArray support (whatever the implementation, through Pavel's new API or simple LED emulation) is in hid-input, we can also simply add a new HID quirk to enable this or not, and use that quirk dynamically (yes, with BPF :-P ) to rebind the device... [0] https://lore.kernel.org/linux-input/20241001-hid-bpf-hid-generic-v3-0-2ef1019468df@xxxxxxxxxx/T/#t
