Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 20 Mar 2024 12:33:44 +0100 | Subject | Re: Future handling of complex RGB devices on Linux v3 | From | Werner Sembach <> |
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Am 20.03.24 um 12:16 schrieb Werner Sembach: > Hi Hans and the others, > > Am 22.02.24 um 14:14 schrieb Werner Sembach: >> Hi, >> >> Thanks everyone for the exhaustive feedback. And at least this thread is a >> good comprehesive reference for the future ^^. >> >> To recap the hopefully final UAPI for complex RGB lighting devices: >> >> - By default there is a singular /sys/class/leds/* entry that treats the >> device as if it was a single zone RGB keyboard backlight with no special >> effects. >> >> - There is an accompanying misc device with the sysfs attributes "name", >> "device_type", "firmware_version_string", "serial_number" for device >> identification and "use_leds_uapi" that defaults to 1. >> >> - If set to 0 the /sys/class/leds/* entry disappears. The driver should >> keep the last state the backlight was in active if possible. >> >> - If set 1 it appears again. The driver should bring it back to a static >> 1 zone setting while avoiding flicker if possible. >> >> - If the device is not controllable by for example hidraw, the misc device >> might also implement additional ioctls or sysfs attributes to allow a more >> complex low level control for the keyboard backlight. This is will be a >> highly vendor specific UAPI. > So in the OpenRGB issue thread > https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/dynamic-lighting-devices > aka HID LampArray was mentioned. I did dismiss it because I thought that is > only relevant for firmware, but I now stumbled upon the Virtual HID Framework > (VHF) > https://learn.microsoft.com/en-us/windows-hardware/drivers/hid/virtual-hid-framework--vhf- > and now I wonder if an equivalent exists for Linux? A quick search did not > yield any results for me. Is this what I have been searching for? https://docs.kernel.org/usb/gadget_hid.html > > If a virtual HID device is possible and the WMI interface can reasonably be > mapped to the LampArray API this might be the best starting point: > > - Implement a Virtual HID device with LampArray > > - Implement LampArray in OpenRGB > > - (Optional) Implement a generic LampArray leds subsystem driver that maps to > the single zone control and ads the use_leds_uapi sysfs switch to the virtual > HID device > > - (Optional) Implement vendor specific controls for > AutonomousMode/built-in-firmware-effects via custom HID commands > > - (Optional) Implement Virtual HID devices for actual HID devices that don't > support LampArray in firmware (Open question: How to prevent userspace/OpenRGB > from interacting with original HID when the virtual HID device is not in > AutonomousMode? How to associate the original and virtual HID device to each > other that userspace can easily recognize this relation? Or is it possible to > add virtual HID commands on top of a real HID device, making it look exactly > like the pure virtual devices for userspace?) > > The LampArray API hereby is made with the intention to be used for multi leds > devices, like per-key-backlight keyboards, unlike the leds UAPI. And it is > coming anyway with new RGB devices soon. So it would not conflict with a > "don't introduce unnecessary UAPI interfaces" principle. Are there any plans > already of Wrapping LampArray in some kind ioctl/sysfs API? Or just have it > used via hidraw? Or was there no discussion about it till now? > > Regards, > > Werner > >> >> - The actual logic interacting with this low level UAPI is implemented by >> a userspace driver >> >> Implementation wise: For the creation of the misc device with the >> use_leds_uapi switch a helper function/macro might be useful? Wonder if it >> should go into leds.h, led-class-multicolor.h, or a new header file? >> >> - Out of my head it would look something like this: >> >> led_classdev_add_optional_misc_control( >> struct led_classdev *led_cdev, >> char* name, >> char* device_type, >> char* firmware_version_string, >> char* serial_number, >> void (*deregister_led)(struct led_classdev *led_cdev), >> void (*reregister_led)(struct led_classdev *led_cdev)) >> >> Let me know your thoughts and hopefully I can start implementing it soon for >> one of our devices. >> >> Kind regards, >> >> Werner Sembach >>
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