Backlight control broken on Lenovo Ideapad Z570

Hi, unfortunately I moved to San Francisco and left my old laptop at home, so I cannot debug the issue anymore. As far as I remember correctly, the problem was that I only had the intel_backlight interface which did not work as expected (value always on top, the buttons did not work, neither did writing the value manually). Once I blacklisted the intel_backlight using the patch I submitted I was able to get the backlight working.

However, I'm reading that you've got fix for the problem and my patch conflicts with it? If this is the case, please replace my code with your fix, and once I get back home (April 28th) we can continue debugging the issue using my laptop.

Best wishes,
Stepan

Quoted 48 lines · Hans de Goede

Hi Stepan,

I'm mailing you because you are the author of:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a11d342f

I've been debugging the same problem together with a Fedora user:
https://bugzilla.redhat.com/show_bug.cgi?id=1187004

And for him your fix does not work, before your fix landed we already came to the conclusion that to fix this we need to disable both the acpi_video backlight interface as well as the ideapad-laptop interface.

Your patch only disables the acpi_video backlight interface (and as a side effect actually enables the ideapad-laptop interface).

I assume that you've a working backlight setup on your Lenovo Ideapad Z570,
can you please do:

ls /sys/class/backlight

And let us know which interfaces show up there. Either you do have a working
ideapad_laptop interface, or you only get intel_backlight and for some reason
ideapad_laptop is not loading on your system (not enabled in your kernel config,
or blacklisted?).

If you only have intel_backlight then that explains why things are not working
for Be (the author of the Fedora bugreport), if you do have an ideapad_laptop
interface and that does work for you, then it seems that not all Lenovo Ideapad Z570-s are created equal. In that case can you please blacklist
the ideapad-laptop module, reboot and see if things still work for you when
using intel_backlight to control the backlight? Once we've a confirmation that either you are already using intel_backlight, or that intel_backlight also
works on your Ideapad, then I'll write a patch to replace yours which leaves
only intel_backlight even if the ideapad-laptop driver gets loaded.

Thanks & Regards,

Hans

Hi, unfortunately I moved to San Francisco and left my old laptop at home, so I cannot debug the issue anymore. As far as I remember correctly, the problem was that I only had the intel_backlight interface which did not work as expected (value always on top, the buttons did not work, neither did writing the value manually). Once I blacklisted the intel_backlight using the patch I submitted I was able to get the backlight working.

However, I'm reading that you've got fix for the problem and my patch conflicts with it? If this is the case, please replace my code with your fix, and once I get back home (April 28th) we can continue debugging the issue using my laptop.

Best wishes,
Stepan

Quoted 48 lines · Hans de Goede

Hi Stepan,

I'm mailing you because you are the author of:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a11d342f

I've been debugging the same problem together with a Fedora user:
https://bugzilla.redhat.com/show_bug.cgi?id=1187004

And for him your fix does not work, before your fix landed we already came to the conclusion that to fix this we need to disable both the acpi_video backlight interface as well as the ideapad-laptop interface.

Your patch only disables the acpi_video backlight interface (and as a side effect actually enables the ideapad-laptop interface).

I assume that you've a working backlight setup on your Lenovo Ideapad Z570,
can you please do:

ls /sys/class/backlight

And let us know which interfaces show up there. Either you do have a working
ideapad_laptop interface, or you only get intel_backlight and for some reason
ideapad_laptop is not loading on your system (not enabled in your kernel config,
or blacklisted?).

If you only have intel_backlight then that explains why things are not working
for Be (the author of the Fedora bugreport), if you do have an ideapad_laptop
interface and that does work for you, then it seems that not all Lenovo Ideapad Z570-s are created equal. In that case can you please blacklist
the ideapad-laptop module, reboot and see if things still work for you when
using intel_backlight to control the backlight? Once we've a confirmation that either you are already using intel_backlight, or that intel_backlight also
works on your Ideapad, then I'll write a patch to replace yours which leaves
only intel_backlight even if the ideapad-laptop driver gets loaded.

Thanks & Regards,

Hans