Comment 292 for bug 1098216

(In reply to edm from comment #165)
> Hi,
> Thinkpad T430 here (without the s), I'm using linux 3.13.4 and systemd 208
> from arch linux booting in bios mode with the last bios update (2.62).
>
> The bug seems the same as for T430s and I can "fix" it with
> acpi_osi='!Windows 2012' or using video.use_native_backlight=1 as kernel
> command line in grub.
>
> It works kinda well with video.use_native_backlight=1 except that I have now
> 4437 level of brightness in /sys/class/backlight/intel_backlight and as
> reported by Weber, systemd complains about this:
>
> [ 9.226063] thinkpad_acpi: Unsupported brightness interface, please
> contact <email address hidden>

This is harmless, I'll send a patch to fix this.

>
>
> System Information
> Manufacturer: LENOVO
> Product Name: 2349KDG
> Version: ThinkPad T430
> (...)
> Wake-up Type: Power Switch
> SKU Number: LENOVO_MT_2349
> Family: ThinkPad T430
>
> It is because of so many levels of backlight that I have in KDE this
> behavior switching brightness with the keys:
> from 0 to 100: 0-10-20-30-40-50-60-70-80-90-100
> from 100 to 0: 100-89-79-69...etc.

I'll prepare a new patch for your laptop later(together with some other model once that model is confirmed to work well with video.use_native_backlight=1).