How to control power of a device from sysfs ?

[Brian Masney]

On Mon, Dec 05, 2016 at 09:26:27AM +0200, Ran Shalit wrote:
> Hello,
> 
> I am trying to turn off screen using sysfs entries,
> but I'm having some difficulties with it:
> 
> 1.
> command:
> echo 0 > /sys/devices/platform/s5p-dsim.0/ea8061/backlight/panel/brightness
> result:
> screen is dimmed - BUT not turned off
> 
> 2.
> command:
> cat
> /sys/devices/platform/s5p-dsim.0/ea8061/backlight/panel/actual_brightness
> 20
> 
> This strengthen the fast that we didn't turned off brightness completely
> 
> 3. In this point I though that maybe I can turn off the whole brightness
> device
> 
> ls /sys/devices/platform/s5p-dsim.0/ea8061/backlight/panel/
>                     actual_brightness
> auto_brightness
> bl_power
> brightness
> device
> dimming
> max_brightness
> power
> subsystem
> type
> uevent
> 
> I made some trials , but didn't made it turned off yet.
> Is there any idea if it's possible to turn it off completely ?

If the driver supports power management, then you can control the power
state with the power/runtime_status sysfs entry. Some of the sysfs
entries in the power/ directory are documented in
Documentation/ABI/testing/sysfs-devices-power.

Brian