diff options
| -rw-r--r-- | drivers/acpi/video_detect.c | 39 |
1 files changed, 23 insertions, 16 deletions
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c index fb49b8f4523a..cc9d0d91e268 100644 --- a/drivers/acpi/video_detect.c +++ b/drivers/acpi/video_detect.c @@ -537,16 +537,6 @@ static const struct dmi_system_id video_detect_dmi_table[] = { /* * Determine which type of backlight interface to use on this system, * First check cmdline, then dmi quirks, then do autodetect. - * - * The autodetect order is: - * 1) Is the acpi-video backlight interface supported -> - * no, use a vendor interface - * 2) Is this a win8 "ready" BIOS and do we have a native interface -> - * yes, use a native interface - * 3) Else use the acpi-video interface - * - * Arguably the native on win8 check should be done first, but that would - * be a behavior change, which may causes issues. */ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native) { @@ -569,19 +559,36 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native) native_available = true; mutex_unlock(&init_mutex); + /* + * The below heuristics / detection steps are in order of descending + * presedence. The commandline takes presedence over anything else. + */ if (acpi_backlight_cmdline != acpi_backlight_undef) return acpi_backlight_cmdline; + /* DMI quirks override any autodetection. */ if (acpi_backlight_dmi != acpi_backlight_undef) return acpi_backlight_dmi; - if (!(video_caps & ACPI_VIDEO_BACKLIGHT)) - return acpi_backlight_vendor; - - if (acpi_osi_is_win8() && native_available) - return acpi_backlight_native; + /* On systems with ACPI video use either native or ACPI video. */ + if (video_caps & ACPI_VIDEO_BACKLIGHT) { + /* + * Windows 8 and newer no longer use the ACPI video interface, + * so it often does not work. If the ACPI tables are written + * for win8 and native brightness ctl is available, use that. + * + * The native check deliberately is inside the if acpi-video + * block on older devices without acpi-video support native + * is usually not the best choice. + */ + if (acpi_osi_is_win8() && native_available) + return acpi_backlight_native; + else + return acpi_backlight_video; + } - return acpi_backlight_video; + /* No ACPI video (old hw), use vendor specific fw methods. */ + return acpi_backlight_vendor; } enum acpi_backlight_type acpi_video_get_backlight_type(void) |