Hardware-controlled LEDs returning ENODATA produce "End-of-file" warnings during unrelated device operations

[farblos]

My system got Linux kernel 7.2 recently on Debian testing:

[~]$ uname -a
Linux host01 7.2.6+deb14-amd64 #1 SMP PREEMPT_DYNAMIC Debian 7.2.6-1 (2026-09-16) x86_64 GNU/Linux

Since then brightnessctl reports error messages like this (note also the missing newline character):

[~]$ brightnessctl -l
End-of-file reading brightness of device 'chromeos:multicolor:right'.End-of-file reading brightness of device 'chromeos:multicolor:left'.End-of-file reading brightness of device 'chromeos:multicolor:power'.Available devices:
Device 'intel_backlight' of class 'backlight':
        Current brightness: 14400 (15%)
        Max brightness: 96000
[...]

Seems that 7.2 comes with commit b819dc7 that lets sysfs report ENODATA for brightness of hardware controlled LED:

[~]$ cat /sys/class/leds/chromeos:multicolor:left/brightness
cat: '/sys/class/leds/chromeos:multicolor:left/brightness': No data available

brightnessctl probably should catch that special case and handle it more gracefully, instead of writing a rather misleading error message?

Thanks!

[farblos]

As a work-around on my particular device, where I don't care about controlling the multi-color LEDs, I can blacklist leds_cros_ec.

[Hummer12007]

@farblos do you know how to detect the case that it's hardware-controlled from userspace apart from catching ENODATA?