On Monday, October 7, 2019 5:48:18 PM CEST Kacper Piwiński wrote: > commit: > efaa14c > > "Starting from win8, MS backlight control driver will set bit 2 of the > parameter of control method _DOS, to inform firmware it should not > perform any automatic brightness changes. This mostly affects hotkey > notification deliver - if we do not set this bit, on hotkey press, > firmware may choose to adjust brightness level instead of sending out > notification and doing nothing." > > win7: > https://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/BrightnessCtrl.docx > > "To avoid problems that might occur if both the system firmware and > the monitor driver control the brightness of the display, the display > miniport driver should set bit 2 of the argument to the _DOS method. > Setting this bit notifies the system firmware that it should not > perform any automatic display brightness changes. The WDDM > driver must set this particular bit because it controls the _DOS > method. The other bits in the _DOS method control the behavior of > the firmware in response to the display switch hot keys." > > win8: > http://read.pudn.com/downloads193/doc/907411/Brightness.doc > > Signed-off-by: Kacper Piwiński <cosiekvfj@xxxxx> > --- > drivers/acpi/acpi_video.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c > index 4f325e47519f..2f380e7381d6 100644 > --- a/drivers/acpi/acpi_video.c > +++ b/drivers/acpi/acpi_video.c > @@ -699,9 +699,13 @@ acpi_video_device_EDID(struct acpi_video_device *device, > * event notify code. > * lcd_flag : > * 0. The system BIOS should automatically control the brightness level > - * of the LCD when the power changes from AC to DC > + * of the LCD when: > + * - the power changes from AC to DC (ACPI appendix B) > + * - a brightness hotkey gets pressed (implied by Win7/8 backlight docs) > * 1. The system BIOS should NOT automatically control the brightness > - * level of the LCD when the power changes from AC to DC. > + * level of the LCD when: > + * - the power changes from AC to DC (ACPI appendix B) > + * - a brightness hotkey gets pressed (implied by Win7/8 backlight docs) > * Return Value: > * -EINVAL wrong arg. > */ > Applying as 5.5 material, thanks!
