Il 05/06/2011 07:31, Mattia Dongili ha scritto:
To my understanding, SNC will receive GPEs in two cases under managed
mode:
1. when the user request a backlight change via the standard acpi_video
2. when ambient light changes
Right, more in detail:
When managed mode is set to 1, automatic backlight is desired by the
user and a userspace tool is supposed to take control of every backlight
change, to be applied via als_backlight node (which offers a fine grain
backlight control for smooth transitions). It will receive two different
types of ALS events, depending on the source of the event, as you said:
1 - ambient light change 2 - backlight change request via backlight
device (in linux, the standard acpi_video backlight device). When either
of the two events occurs, this software will calculate a new backlight
level (using a model specific formula) and set it by writing in the
als_backlight file mentioned earlier. (NOTE: this is how the hardware
has been designed and it supposed to work even though workarounds are
possible).
When managed mode is set to 0, no automatic backlight control is
requested by the user and no userspace software is doing any backlight
regulation based on the ALS readings. This implies that no ALS events
are generated (regardless the source) and the standard ACPI backlight
methods (used by the acpi_video backlight device) will work properly as
usual.
In both cases your code sends an acpi event to userspace. Let alone the
acpi event discussion that belongs to another thread, why aren't we
just setting the requested brightness?
Simply because any calculation can be done in userspace, but if we can
include the calculation stuff inside the driver, then we can get rid of
the daemon, everything will be easier and we can avoid the als_backlight
file too. Is it possible? The formulas are a bit complex but just a few
lines of code, while the keyboard backlight based on the ambient light
is just a matter of a threshold check.
--
To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
