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.
- 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
