Public bug reported:
Binary package hint: gnome-power-manager
When gnome-power-manager dims the screen when on battery or when idle, the
backlight turns entirely off.
In addition, during the fade the screen blinks: 100%, OFF, 75%, OFF, 50%, OFF.
cat /proc/acpi/video/VGA/LCD/brightness:
levels: 100 37 12 25 37 50 62 75 87 100
current: 100
The screen is turning off whenever something requests a brightness level
between the available discrete levels; thus the default dim-when-
inactive brightness of 30 turns the backlight off. For a while, I
thought my system was freezing at a black screen at login (battery) or
idle (AC), until I remembered the brightness controls.
One factor in this is the new /sys/class/backlight/ interface for brightness
control, common to all ACPI drivers:
This structure does not seem to provide the same, necessary information, such
as available discrete brightness levels.
/sys/class/backlight/acpi_video0/max_brightness: 100
/sys/class/backlight/acpi_video0/actual_brightness: 62 <== changes even
when keyboard hotkeys are used; g-p-m does not notice this.
/sys/class/backlight/acpi_video0/brightness: 62 <== changes
only when software requests a change.
HAL lists num_levels=101, while ideally it should be 8 or 9. Better yet, the
kernel itself should provide the discrete levels, or rounding issues may appear.
Oddly. the brightness levels 12, 37, 62, and 75 work through echoing into
'brightness', but turn the backlight off if used in g-p-m.
Echoing invalid values there turns the backlight off, but echoing into the
/proc structure returns 'invalid argument'.
Note: the data under /sys/class/backlight is not synchronized with
/proc/acpi/video; for consistency, it should be.
(My DSDT also provides sys/class/backlight/acpi_video1/ and
/proc/acpi/video/GFX0/DD0n/ for n from 1 to 5; LCD is 4. However, I
would not expect the values there to be synchronized with acpi_video0
and VGA/LCD.)
** Affects: gnome-power-manager (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux-source-2.6.22 (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux-source-2.6.22 (Ubuntu)
Importance: Undecided
Status: New
** Summary changed:
- LCD backlight turns entirely off when set between brightness levels.
+ LCD backlight turns off between brightness levels.
** Description changed:
Binary package hint: gnome-power-manager
When gnome-power-manager dims the screen when on battery or when idle, the
backlight turns entirely off.
In addition, during the fade the screen blinks: 100%, OFF, 75%, OFF, 50%, OFF.
cat /proc/acpi/video/VGA/LCD/brightness:
levels: 100 37 12 25 37 50 62 75 87 100
current: 100
The screen is turning off whenever something requests a brightness level
between the available discrete levels; thus the default dim-when-
inactive brightness of 30 turns the backlight off. For a while, I
thought my system was freezing at a black screen at login (battery) or
idle (AC), until I remembered the brightness controls.
One factor in this is the new /sys/class/backlight/ interface for brightness
control, common to all ACPI drivers:
- This structure does not seem to provide the same information as the all the
necessary information, such as available discrete brightness levels.
+ This structure does not seem to provide the same, necessary information, such
as available discrete brightness levels.
/sys/class/backlight/acpi_video0/max_brightness: 100
/sys/class/backlight/acpi_video0/actual_brightness: 62 <== changes even
when keyboard hotkeys are used; g-p-m does not notice this.
/sys/class/backlight/acpi_video0/brightness: 62 <== changes
only when software requests a change.
- HAL lists num_levels=101, while ideally it should be 8 or 9. Better yet, the
kernel itself should provide the discrete levels -- otherwise, rounding issues
may appear.
+ HAL lists num_levels=101, while ideally it should be 8 or 9. Better yet, the
kernel itself should provide the discrete levels, or rounding issues may appear.
Oddly. the brightness levels 12, 37, 62, and 75 work through echoing into
'brightness', but turn the backlight off if used in g-p-m.
Echoing invalid values there turns the backlight off, but echoing into the
/proc structure returns 'invalid argument'.
Note: the data under /sys/class/backlight is not synchronized with
/proc/acpi/video; for consistency, it should be.
My DSDT also provides acpi_video1/ corresponding to n=4 of
/proc/acpi/video/GFX0/DD0n/; however, I would not expect the values there to be
synchronized with acpi_video0/ and VGA/LCD/, respectively.
** Description changed:
Binary package hint: gnome-power-manager
When gnome-power-manager dims the screen when on battery or when idle, the
backlight turns entirely off.
In addition, during the fade the screen blinks: 100%, OFF, 75%, OFF, 50%, OFF.
- cat /proc/acpi/video/VGA/LCD/brightness:
- levels: 100 37 12 25 37 50 62 75 87 100
- current: 100
+ cat /proc/acpi/video/VGA/LCD/brightness:
+ levels: 100 37 12 25 37 50 62 75 87 100
+ current: 100
The screen is turning off whenever something requests a brightness level
between the available discrete levels; thus the default dim-when-
inactive brightness of 30 turns the backlight off. For a while, I
thought my system was freezing at a black screen at login (battery) or
idle (AC), until I remembered the brightness controls.
One factor in this is the new /sys/class/backlight/ interface for brightness
control, common to all ACPI drivers:
This structure does not seem to provide the same, necessary information, such
as available discrete brightness levels.
- /sys/class/backlight/acpi_video0/max_brightness: 100
- /sys/class/backlight/acpi_video0/actual_brightness: 62 <== changes even
when keyboard hotkeys are used; g-p-m does not notice this.
- /sys/class/backlight/acpi_video0/brightness: 62 <== changes
only when software requests a change.
+ /sys/class/backlight/acpi_video0/max_brightness: 100
+ /sys/class/backlight/acpi_video0/actual_brightness: 62 <== changes
even when keyboard hotkeys are used; g-p-m does not notice this.
+ /sys/class/backlight/acpi_video0/brightness: 62 <==
changes only when software requests a change.
HAL lists num_levels=101, while ideally it should be 8 or 9. Better yet, the
kernel itself should provide the discrete levels, or rounding issues may appear.
Oddly. the brightness levels 12, 37, 62, and 75 work through echoing into
'brightness', but turn the backlight off if used in g-p-m.
Echoing invalid values there turns the backlight off, but echoing into the
/proc structure returns 'invalid argument'.
- Note: the data under /sys/class/backlight is not synchronized with
/proc/acpi/video; for consistency, it should be.
- My DSDT also provides acpi_video1/ corresponding to n=4 of
/proc/acpi/video/GFX0/DD0n/; however, I would not expect the values there to be
synchronized with acpi_video0/ and VGA/LCD/, respectively.
+ Note: the data under /sys/class/backlight is not synchronized with
+ /proc/acpi/video; for consistency, it should be.
+
+ (My DSDT also provides sys/class/backlight/acpi_video1/ and
+ /proc/acpi/video/GFX0/DD0n/ for n from 1 to 5; LCD is 4. However, I
+ would not expect the values there to be synchronized with acpi_video0
+ and VGA/LCD.)
** Summary changed:
- LCD backlight turns off between brightness levels.
+ LCD backlight turns off when at idle, on battery, or between brightness
levels.
** Summary changed:
- LCD backlight turns off when at idle, on battery, or between brightness
levels.
+ LCD backlight turns off when at idle or on battery.
--
LCD backlight turns off when at idle or on battery.
https://bugs.launchpad.net/bugs/121833
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