On the Intel GM45/GMA 4500MHD laptop with Debian Sid/unstable and Linux 5.6.7 and GNOME Shell 3.36.2, trying to change the brightness of the internal display using the function keys, GNOME shows the OSD, which seems to have five levels (from acer_wmi?), but the actual brightness does *not* change. There is only `/sys/class/backlight/intel_backlight/brightness` though, and writing values to it seems to work. Booting the system with `acpi_backlight=vendor`, exposes `/sys/devices/platform/acer-wmi/backlight/acer-wmi/brightness`, but the behavior is the same. Booting the system with `acpi_backlight=native` or `acpi_backlight=native`, changing the brightness with the function keys works, and there now seem to be 15 (or 16) levels. ``` $ grep '.*' /sys/class/dmi/id/*_* 2> /dev/null /sys/class/dmi/id/bios_date:07/26/2011 /sys/class/dmi/id/bios_vendor:Acer /sys/class/dmi/id/bios_version:V1.14 /sys/class/dmi/id/board_asset_tag:Base Board Asset Tag /sys/class/dmi/id/board_name:BA51_MV /sys/class/dmi/id/board_vendor:Acer /sys/class/dmi/id/board_version:V1.14 /sys/class/dmi/id/chassis_asset_tag: /sys/class/dmi/id/chassis_type:10 /sys/class/dmi/id/chassis_vendor:Acer /sys/class/dmi/id/chassis_version:V1.14 /sys/class/dmi/id/product_family:Intel_Mobile /sys/class/dmi/id/product_name:TravelMate 5735Z /sys/class/dmi/id/product_sku:Montevina_Fab /sys/class/dmi/id/product_version:V1.14 /sys/class/dmi/id/sys_vendor:Acer ```
Created attachment 289201 [details] ACPI: video: Use native backlight on Acer TravelMate 5735Z From commit 1c8fbc1f9b (ACPI: video: Use native backlight on Acer Aspire 5783z): > The Acer Aspire 5783z shipped with Windows 7 and as such does not trigger our > "win8 ready" heuristic for preferring the native backlight interface. I do not know about the “win8 ready” heuristic, but this laptop also shipped with Windows 7 (at least it has such a sticker on it). So I attach a similar patch and mention it in the commit message too.
Created attachment 289203 [details] ACPI: video: Use native backlight on Acer TravelMate 5735Z Add bug report URL in a comment.
Hi Paul, Thank you for the bug-report and the patch. Can you please submit the patch upstream using the standard Linux kernel patch submission process? : https://www.kernel.org/doc/html/latest/process/submitting-patches.html
Note the attached-patch looks fine, you just need to "git send-email" it: To: Rafael J. Wysocki" <rjw@rjwysocki.net> Len Brown <lenb@kernel.org> Cc: linux-acpi@vger.kernel.org And since I've just reviewed it and it looks good to me, you may also add my: Reviewed-by: Hans de Goede <hdegoede@redhat.com> Just add that line to the commit message directly above your Signed-off-by before sending out the patch.
Patch merged in upstream commit c41c36e900a337b4132b12ccabc97f5578248b44 Author: Paul Menzel <pmenzel@molgen.mpg.de> AuthorDate: Fri May 22 14:22:28 2020 +0200 Commit: Rafael J. Wysocki <rafael.j.wysocki@intel.com> CommitDate: Mon May 25 11:58:51 2020 +0200 ACPI: video: Use native backlight on Acer TravelMate 5735Z Currently, changing the brightness of the internal display of the Acer TravelMate 5735Z does not work. Pressing the function keys or changing the slider, GNOME Shell 3.36.2 displays the OSD (five steps), but the brightness does not change. The Acer TravelMate 5735Z shipped with Windows 7 and as such does not trigger our "win8 ready" heuristic for preferring the native backlight interface. Still ACPI backlight control doesn't work on this model, where as the native (intel_video) backlight interface does work by adding `acpi_backlight=native` or `acpi_backlight=none` to Linux’ command line. So, add a quirk to force using native backlight control on this model. Link: https://bugzilla.kernel.org/show_bug.cgi?id=207835 Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>