From: Hans de Goede <hidden> Date: 2014-05-02 09:32:25
Hi All,
I was already considering asking for $subject for a while, but I did not see
any bug reports caused by it so I didn't ask. Until today I discovered that
I'm not seeing any bugs because Fedora is carrying a kernel patch
changing the default.
A quick google search for brightness_switch_enabled OTOH reveals that for
other distros it is a serious problem, see ie:
https://bugs.launchpad.net/gnome-settings-daemon/+bug/527157http://askubuntu.com/questions/173921/why-does-my-thinkpad-brightness-control-skip-steps
The problem is that acpi-video is unique in that it not only generates
brightness up/down keypresses, but also (sometimes) actively changes the
brightness itself.
This presents an inconsistent kernel interface to userspace, basically there
are 2 different scenarios, depending on the laptop model:
1) On some laptops a brightness up/down keypress means: show a brightness osd
with the current brightness, iow it is a brightness has changed notification.
2) Where as on (a lot of) other laptops it means a brightness up/down key was
pressed, deal with it.
Most of the desktop environments interpret any press as in scenario 2, and
change the brightness up / down as a response to the key events, causing it
to be changed twice, once by acpi-video and once by the DE.
With the new default for video.use_native_backlight we will be moving even
more laptops over to behaving as in scenario 2. Making the remaining laptops
even more of a weird exception. Also note that it is hard to detect scenario
1 properly in userspace, and AFAIK none of the DE-s deasls with it.
Therefor I would like to propose to change the brightness_switch_enabled
default to 0.
Regards,
Hans
From: Rafael J. Wysocki <hidden> Date: 2014-05-02 11:40:18
On Friday, May 02, 2014 11:32:15 AM Hans de Goede wrote:
Hi All,
I was already considering asking for $subject for a while, but I did not see
any bug reports caused by it so I didn't ask. Until today I discovered that
I'm not seeing any bugs because Fedora is carrying a kernel patch
changing the default.
A quick google search for brightness_switch_enabled OTOH reveals that for
other distros it is a serious problem, see ie:
https://bugs.launchpad.net/gnome-settings-daemon/+bug/527157http://askubuntu.com/questions/173921/why-does-my-thinkpad-brightness-control-skip-steps
The problem is that acpi-video is unique in that it not only generates
brightness up/down keypresses, but also (sometimes) actively changes the
brightness itself.
This presents an inconsistent kernel interface to userspace, basically there
are 2 different scenarios, depending on the laptop model:
1) On some laptops a brightness up/down keypress means: show a brightness osd
with the current brightness, iow it is a brightness has changed notification.
2) Where as on (a lot of) other laptops it means a brightness up/down key was
pressed, deal with it.
Most of the desktop environments interpret any press as in scenario 2, and
change the brightness up / down as a response to the key events, causing it
to be changed twice, once by acpi-video and once by the DE.
With the new default for video.use_native_backlight we will be moving even
more laptops over to behaving as in scenario 2. Making the remaining laptops
even more of a weird exception. Also note that it is hard to detect scenario
1 properly in userspace, and AFAIK none of the DE-s deasls with it.
Therefor I would like to propose to change the brightness_switch_enabled
default to 0.
Aaron, what do you think about that?
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
On Friday, May 02, 2014 11:32:15 AM Hans de Goede wrote:
quoted
Hi All,
I was already considering asking for $subject for a while, but I did not see
any bug reports caused by it so I didn't ask. Until today I discovered that
I'm not seeing any bugs because Fedora is carrying a kernel patch
changing the default.
A quick google search for brightness_switch_enabled OTOH reveals that for
other distros it is a serious problem, see ie:
https://bugs.launchpad.net/gnome-settings-daemon/+bug/527157http://askubuntu.com/questions/173921/why-does-my-thinkpad-brightness-control-skip-steps
The problem is that acpi-video is unique in that it not only generates
brightness up/down keypresses, but also (sometimes) actively changes the
brightness itself.
This presents an inconsistent kernel interface to userspace, basically there
are 2 different scenarios, depending on the laptop model:
1) On some laptops a brightness up/down keypress means: show a brightness osd
with the current brightness, iow it is a brightness has changed notification.
2) Where as on (a lot of) other laptops it means a brightness up/down key was
pressed, deal with it.
Most of the desktop environments interpret any press as in scenario 2, and
change the brightness up / down as a response to the key events, causing it
to be changed twice, once by acpi-video and once by the DE.
With the new default for video.use_native_backlight we will be moving even
more laptops over to behaving as in scenario 2. Making the remaining laptops
even more of a weird exception. Also note that it is hard to detect scenario
1 properly in userspace, and AFAIK none of the DE-s deasls with it.
Therefor I would like to propose to change the brightness_switch_enabled
default to 0.
Aaron, what do you think about that?
Personally, I like this.
Last time I remembered, people who do not use GUI or use a simple GUI which
does not provide handling of backlight events prefer to having this param
default to 1(and they have a working acpi_video interface of course). But I
suppose most people are using a GUI that handles such events and the in
kernel handling of backlight events is indeed unique for acpi_video and
cause in consistence with other backlight control interfaces, I think it is
a good thing to set brightness_switch_enabled to 0 by default.
Thanks,
Aaron