I tried to boot to linux-image-4.4.0-62-generic but I could not get past the login screen. So I reinstalled the linux-image-4.4.0-62-generic and run update-grub. Then I could boot to it (linux-image-4.4.0-62-generic) and the brightness is working again. I think it is a kernel regression.
I tried to boot to linux-image- 4.4.0-62- generic but I could not get past the login screen. So I reinstalled the linux-image- 4.4.0-62- generic and run update-grub. Then I could boot to it (linux- image-4. 4.0-62- generic) and the brightness is working again. I think it is a kernel regression.