[Bug 288180] New: Enhance backlight detection in powerdevil/backend/upower/backlighthelper.cpp

[Corentin Chary]

https://bugs.kde.org/show_bug.cgi?id=288180

           Summary: Enhance backlight detection in
                    powerdevil/backend/upower/backlighthelper.cpp
           Product: kde
           Version: unspecified
          Platform: Unlisted Binaries
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: wishlist
          Priority: NOR
         Component: general
        AssignedTo: unassigned-bugs at kde.org
        ReportedBy: corentin.chary at gmail.com


Version:           unspecified (using Devel) 
OS:                Linux

Currently the code maintain a whitelist of backlight:


    interfaces << "nv_backlight" << "intel_backlight" << "radeon_bl" <<
"mbp_backlight"
               << "asus_laptop" << "toshiba" << "eeepc" << "thinkpad_screen" <<
"acpi_video1"
               << "acpi_video0" << "apple_backlight" << "fujitsu-laptop" <<
"samsung"
               << "nvidia_backlight" << "dell_backlight" << "sony"
               ;

The issue is that this has to be updated each time a new driver is added to the
kernel. For example the list lacks: "asus-nb-wmi" and "asus-wmi".

This whitelist also provides some priority information (use gpu first, then
acpi, then vendor...).

Instead, we could use a new backlight attribute (if present):

What:           /sys/class/backlight/<backlight>/type
Date:           September 2010
KernelVersion:  2.6.37
Contact:        Matthew Garrett <mjg at redhat.com>
Description:
                The type of interface controlled by <backlight>.
                "firmware": The driver uses a standard firmware interface
                "platform": The driver uses a platform-specific interface
                "raw": The driver controls hardware registers directly

                In the general case, when multiple backlight
                interfaces are available for a single device, firmware
                control should be preferred to platform control should
                be preferred to raw control. Using a firmware
                interface reduces the probability of confusion with
                the hardware and the OS independently updating the
                backlight state. Platform interfaces are mostly a
                holdover from pre-standardisation of firmware
                interfaces.

As described, type can be used to describe the preference. However, using the
gpu backlight (intel, radeon, nouveau, nvidia) provide a better control most of
the time, so maybe an hybrid approach should be taken:
- Use a whitelist/priority list (containing only intel, radeon, etc...) ?
- If not found, use a firmware backlight
- If not found, use a platform backlight
- If not found, use a raw backlight

And maybe a settings should allow the user to specify a backlight (something
hidden in a file, no need for a gui to set it).

Reproducible: Didn't try



Expected Results:  
-

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