InkBox OS power daemon

InkBox OS power daemon

Configuration

All configuration is stored in the /data/config/20-sleep_daemon directory. Below is a list and description of the files that are present in that directory.

appsList

This is a list of apps that will be frozen (SIGSTOP) by the power daemon by default before going to sleep, it’s something like this:

inkbox-bin
oobe-inkbox-bin
lockscreen-bin
calculator-bin
qreversi-bin
2048-bin
scribble
lightmaps

It will be created as a fallback, but it should be created before.

1-cinematicBrightnessDelayMs

This file contains an integer that determines how long will be the delay between switching one percent of brightness.
By default, it’s 50. If the file doesn’t exist, it will be created.

2-cpuGovernor

Experimental feature, sets a cpuGovernor at boot, or when variables are updated.
By default, it’s ondemand. the options are: - interactive - conservative - userspace - powersave - ondemand - performance

3-whenChargerSleep

If this file’s content is false, the device will not go to sleep when it’s charged (because some devices can’t). By default it’s different for many devices, because it happens in devices from 2011 to ~2017 (N905B, N905B, N705, N613, N236, N437, KT )

4-whenChargerWakeUp

If this file’s content is true and if the program detects that between going to sleep and after suspending that the device’s charger state changed, it will try to sleep anyway.
By default it’s set to false. If the 3-whenChargerSleep option is set to false, then this option should also be false.

5-wifiReconnect

If this file’s content is true, Wi-Fi will be reconnected on wake-up.
By default, this option is set to true.

6-ledUsage

If this file’s content is true, the following will happen: the power LED will light up for indicating that the device is going to sleep. The blinking goes as follows: - Firstly, slow led blinking indicates invidual steps in preparing to sleep (turn off Wi-Fi, show screensaver, etc.) - Secondly, fast blinking indicates write to state-extended, so all devices components are preparing to sleep - Thirdly, blinking (but faster than in the first step) indicates that the device is trying to sleep, but one of the device’s components (touchscreen propably) refused to. That’s normal behavior, so don’t worry It will also turn it on when the device is charging and will be turned off when the device finishes charging.

7-idleSleep

This file contains an integer that determines, in seconds, when to go to sleep when no touch input is received from the screen. 0 means ‘Never’, minimum is 15 seconds.
By default, it’s set to 60.

8-customCase

This option is complicated, I will try my best to explain it.
If you have a 3D-printed case with a magnet in it, there is a big chance that the magnet will put the device to sleep when you flip the case to the back. This option skips the every one magnet call.
A little visualization: - The device boots up, the case is opened, no magnet contact. This option is enabled. - You flip the case to the back, magnet is close to the hall sensor and triggers it. You don’t want that. With this option, this call will be ignored. - Now you close the case, magnet contacts, the device goes to sleep.

A bit of synchronization is needed, it’s a bit complicated to use but it works, and is great (on the Kobo Nia). It’s just an option, don’t care about it if you don’t want to :)
By default, it’s set to false.

9-deepSleep

This file is only read by the GUI. If it’s set to true (from the GUI power daemon settings) the power menu option of the eReader called ‘Suspend’ will be replaced by ‘Deep sleep’. If this is clicked, /run/ipd/sleepCall will be created and deepSleep will be written to it instead of sleep (as it usually would). In this way inotify will be triggered, and the device will go to sleep, but with extra things, like: - powersave CPU governor, which will extend the time the device takes to wake-up, but the battery will live longer.

updateConfig

If true is written to this file, the daemon will update all its variables on-the-fly, then write false to this file.

Other

Debugging

If the environment variable argument DEBUG is set to true, the daemon will output logs to stdio and /var/log/ipd.log.
You can also enable debug logging from the OS itself, by creating /boot/flags/IPD_DEBUG with the value ‘true’ in it.

Communication

In /run/ipd (which is an 8K temporary filesystem) is a named pipe called fifo. It’s bind-mounted between the main root filesystem and the GUI’s root filesystem (to /kobo/dev/ipd). User applications can access it at /dev/ipd/fifo, it’s read-only.

Instructions for communicating with it:

Messages sent in this named pipe always have a length of 5 bytes. It makes them easier to parse.
Current messages sent by the power daemon: - start indicates that the device is going to sleep. The application has 300 ms to react to this message. Because Qt applications get all touch input at wake-up even if the device is suspended (buffer), which may cause confusion and problems, it’s advised to show a QDialog with exec(), which eats all touch input until its hide() is called. For code examples look into src/widgets/powerDaemon in InkBox source code. - stop0 is called after a device wakes up.

Screensaver

Any image you put in /data/onboard/.screensaver (yes, /data/onboard is the directory where you would usually put books) with the extension .png will be randomly chosen and used as a screensaver. The “Sleeping” text or the image’s size needs to be handled by the user itself. Additional notes: - Yes, you create that directory and yes, it is a hidden directory - If you want a single screensaver, put only one image there - If no image is found, the normal screensaver will be used

Miscellanous notes

• /kobo/tmp/currentlyRunningUserApplication is a file which has the current user application process name, to freeze it
• “Why use sleepCall when you have the named pipe?” I would need to create another thread to watch the named pipe, which is bad because there are already 4 other threads and it gets slowly CPU-heavy.
• The daemon grabs the /dev/input/event0 input device for sanity reasons.